Abstract:
An accelerator module actuated by the driver&#39;s foot for controlling the output of a driving engine or motor of a motor vehicle employs a friction element for generating a friction hysteresis for the purpose of achieving a comfortable driving feel. Support of the pedal lever is completely independent of the generation of the friction hysteresis, resulting in a particularly favorable, especially stable, and play-free support of the pedal lever, and the brake insert for generating the friction hysteresis is particularly easy to manufacture.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 USC 371 application of PCT/DE 01/01575 filed on Apr. 25, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is based on an accelerator pedal module in particular for use in control of an engine. 
     2. Description of the Prior Art 
     Japanese patent application no. 60-99729 (JP-A-60-99729) has disclosed an accelerator pedal module with a pedal lever pivotably supported on a support structure, with a sensor which detects an angular position of the pedal lever and emits a corresponding electrical signal, and with a restoring spring system for restoring the pedal lever to a starting position. A bearing pin can be used to support the pedal lever in a very favorable, precise, and play-free manner on the support structure connected to a vehicle body. 
     Based on the accelerator pedal disclosed in JP-A-60-99729, the object of the invention is to achieve the fact that the pedal lever is precisely supported and that a friction hysteresis occurs when the pedal lever is actuated, where this friction hysteresis should be achieved with simple means and should be precisely definable and in addition, the friction hysteresis should increase with increasing actuation of the pedal lever. 
     U.S. Pat. No. 5,408,899 has disclosed a pedal apparatus in which a number of spacers are provided for the purpose of generating friction and the coils of restoring springs are supported on the spacers. A movement of the pedal lever produces relative movements between the spacers and the restoring springs. As a result, friction is produced between the spacers and the bearing pin, among the various spacers, and also between the spacers and the restoring springs. In this very expensive design, it is disadvantageous that the friction depends very heavily on dimensional tolerances of the components and another disadvantage is the friction between the spacers and the restoring springs because this results in the fact that the restoring springs, which represent a safety-related component, fail particularly easily with extended use. Another disadvantage is that the friction is not directly related to the restoring force. 
     International patent application WO 97/12780 has disclosed an accelerator pedal module in which a semicircle with a relatively large radius is provided on the pedal lever and the support structure has a bearing shell in which the semicircle of the pedal lever is supported. The radius of the semicircle and the bearing shell must be relatively large in order to achieve the desired friction. In this design, it is disadvantageous that the support of the pedal lever and the generation of the desired friction occur directly in the same place. Because the friction surface provided between the semicircle and the bearing shell serves not only to produce the friction force but also to support the pedal lever, very high demands must be placed on the form precision as well as the surface quality and concentricity of the friction surface. In other words, because the support location is used not only to support the pedal lever but also to generate the friction, the structural design must take into account not only support considerations but also frictional considerations. Compromises must therefore be made, as a result of which the entire structure is somewhat unstable and the pedal lever is not supported in a particularly precise manner, which can be detected when the electrical signal is generated at high-resolution. In addition, it is quite expensive to produce the known accelerator pedal module. 
     German patent application DE 4426549 A1 has disclosed an accelerator pedal module in which the pedal lever is supported in two short shell arcs provided with a friction lining. The shell arcs have a relatively large diameter in order to achieve a sufficient friction. Because of the large diameter of the shell arcs and because the shell arcs are relatively short, it must be concluded that in a pedal lever support of this kind, the support of the pedal lever is quite unstable. As a result, a precise electrical signal can hardly be expected with this accelerator pedal module. 
     SUMMARY OF THE INVENTION 
     The accelerator pedal module according to the invention has the advantage over the prior art that for a low cost, a precise support of the pedal lever on the support structure can be achieved and a friction force can be achieved that depends on the actuated pivot angle of the pedal lever. A particular advantage is that the generation of the friction force is achieved by simple means. It is particularly advantageous that the pedal lever support and the friction force generation are achieved by mutually independent means. The means for supporting the pedal lever and the means for generating the friction force can each be optimally designed for their respective purposes. As a result, a high degree of precision can be achieved in the support of the pedal lever. The precise support of the pedal lever has the advantage that a precise electrical signal can be produced that indicates the position of the pedal lever. 
     If two friction surfaces and two friction elements are provided, then this has the advantage that the support of the pedal lever in the vicinity of the support location can be embodied as essentially symmetrical, as a result of which the precision in the support of the pedal lever can be improved even further. In particular, the two friction surfaces and friction elements can be affixed symmetrically with regard to the longitudinal direction of the pedal lever. 
     The crossbar can be used to connect the two friction elements to each other in a very simple manner and the restoring spring system can act on the crossbar. As a result, the entire design is very simple and a uniform distribution of the force of the restoring spring system onto the two friction elements can be advantageously achieved. 
     The coupling lever can advantageously transfer the force of the restoring spring system onto the friction element. 
     If the coupling lever is connected to the support structure in a one-piece, articulating fashion, then this has the advantage that fewer components have to be assembled. 
     If the coupling lever is connected to the friction element in a one-piece, articulating fashion, then this has the advantage that the friction element and the coupling lever can be produced together and fewer components have to be assembled during assembly of the accelerator pedal module. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferably selected, particularly advantageous exemplary embodiments of the invention are described herein below in conjunction with the drawings, in which: 
     FIG. 1 shows a longitudinal section taken on line I—I of FIG. 3, through a first exemplary embodiment of the invention, 
     FIG. 2 shows a detail of the first exemplary embodiment, 
     FIG. 3 shows a cross section through the first exemplary embodiment taken on line III—III of FIG. 1, 
     FIG. 4 shows a longitudinal section through a second exemplary embodiment, 
     FIG. 5 shows details of the second exemplary embodiment, 
     FIG. 6 shows a partial section through the second exemplary embodiment, 
     FIG. 7 shows a partial section through a third exemplary embodiment, 
     FIG. 8 shows a partial section through a fourth exemplary embodiment, 
     FIG. 9 shows a longitudinal section through a fifth exemplary embodiment, and 
     FIG. 10 is a graph that shows the dependence of the actuation force F on the actuation path s of the pedal lever. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The accelerator pedal module  1  embodied according to the invention can be used to control different driving engines. For example, the drive engine is an Otto engine whose throttle valve is adjusted with a servomotor. In this instance, the accelerator pedal module is used to transmit electrical signals which are supplied to the servomotor that adjusts the throttle valve. However, the driving engine can also be a diesel engine or an electric motor, for example; in these cases as well, electrical signals are emitted by the accelerator pedal module  1  which, appropriately transformed, control the output of the driving engine. 
     The accelerator pedal module  1  is preferably fastened to a part of the vehicle directly in the vehicle driver&#39;s range of action. The pedal lever  3  of the accelerator pedal module  1  is frequently also referred to as the gas pedal. 
     In all the figures, parts which are the same or function in the same manner are provided with the same reference numerals. Provided that nothing to the contrary is mentioned or shown in the drawings, that which is mentioned in conjunction with one of the figures and shown in it also applies to the other exemplary embodiments. Provided that nothing to the contrary is stated in the explanations, the details of the different exemplary embodiments can be combined with one another. 
     FIGS. 1,  2 , and  3  show a preferably selected, particularly advantageous first exemplary embodiment. FIG. 1 shows a longitudinal section through the accelerator pedal module  1 . The sectional plane and viewing direction shown in FIG. 1 is labeled I—I in FIG.  3 . FIG. 2 shows the brake insert  10  of the accelerator pedal module  1  before its installation into the accelerator pedal module  1 . FIG. 3 shows a cross section through the accelerator pedal module  1 . The cutting plane and viewing direction shown in FIG. 3 are labeled III—III in FIG.  1 . 
     The accelerator pedal module  1  includes a support structure  2  and a pedal lever  3 . The support structure  2  is embodied in the form of a housing. The support structure  2  has a bottom  2   a , a back  2   b , a top  2   c , a first side wall  2   d , a second side wall  2   e , and an opening  2   f . The pedal lever  3  has a pedal plate  3   a , a shaft  3   b , and a bearing region  3   c . Lateral to the longitudinal direction of the pedal lever  3 , the bearing region  3   c  has a first projection  3   d  and a second projection  3   e  that protrude laterally beyond the bearing region  3   c . In the bearing region  3   c  of the pedal lever  3 , there is a bore  3   g ; and a housing bore  2   g  extends through the side walls  2   d ,  2   e  of the support structure  2 . A bearing pin  6  is inserted into the housing bore  2   g  of the support structure  2  and the bore  3   g  of the pedal lever  3 . The bearing pin  6  is inserted with a press-fit into the bearing region  3   c  of the pedal lever  3  and is inserted with a slight press-fit into the first side wall  2   d  and into the second side wall  2   e  of the support structure  2 . The bearing pin  6  assures that the pedal lever  3  is supported so that it can pivot on the support structure  2  in a precise and exact manner without wobbling. 
     The support structure  2  is fastened to a body part  8  of a motor vehicle. The bearing region  3   c  of the pedal lever  3  is disposed inside the housing-like support structure  2 . The shaft  3   b  of the pedal lever  3  protrudes out of the support structure  2  through the opening  2   f . The pedal plate  3   a  is disposed at the protruding end of the shaft  3   b.    
     A brake insert  10  is provided in the accelerator pedal module  1 . The brake insert  10  is shown separately in an oblique view in FIG.  2 . 
     In the selected exemplary embodiment for FIGS. 1,  2 , and  3 , the brake insert  10  is essentially comprised of a first friction element  11 , a second friction element  12 , and a crossbar  14 . The friction element  11  has a bottom linkage point  11   a , a friction region  11   b , and a spring-side linkage point  11   c . The friction region  11   b  is disposed approximately half the distance between the two linkage points  11   a  and  11   c . The second friction element  12  is embodied as the mirror image of the friction element  11  and works in parallel with the friction element  11 . The second friction element  12  has a bottom linkage point  12   a , a friction region  12   b , and a spring-side linkage point  12   c . The second friction region  12   b  is disposed approximately half the distance between the two linkage points  12   a  and  12   c . The crossbar  14  connects the spring-side linkage point  11   c  of the friction element  11  to the spring-side linkage point  12   c  of the second friction element  12 . In the center, between the two friction elements  11 ,  12 , there is a spring linkage point  16  embodied in the form of a blind bore in the crossbar  14 . The crossbar  14  connects the spring-side linkage point  11   c  to the spring-side linkage point  12   c . As is shown particularly by FIG. 2, in the exemplary embodiment shown in FIGS. 1,  2 , and  3 , the brake insert  10  that includes the friction elements  11 ,  12  and the crossbar  14  is embodied as one piece. The entire brake insert  10  can be produced together in a single mold by means of injection molding. 
     The support structure  2  contains a support surface  18  oriented away from the pedal lever  3 . 
     At the projection  3   d  of the pedal lever  3 , there is a friction surface  21  concentric to the bearing pin  6 ; and a second friction surface  22  is provided on the second projection  3   e  of the pedal lever  3 , concentric to the bearing pin  6 . 
     The bottom linkage point  11   a  of the friction element  11  is attached to the support surface  18  of the support structure  2 . In other words, the bottom linkage point  11   a  and the support surface  18  are provided so that the friction element  11  can be suspended on the support structure  2  and secured by it. The friction surface  21  of the pedal lever  3  points away from the bottom  2   a  of the support structure  2 . The friction region  11   b  of the friction element  11  rests against the friction surface  21  of the pedal lever  3 . The bottom linkage point  11   a  and the spring-side linkage point  11   c  protrude beyond the friction surface  21 . The friction surface  21  and the friction region  11   b  are disposed between the bottom linkage point  11   a  and the spring-side linkage point  11   c.    
     The pedal lever  3  can be adjusted between a non-actuated starting position R and a completely actuated end position E. The pedal lever  3  is shown in its starting position R. Individual regions of the pedal lever  3  are also indicated with dashed lines in FIG. 1, when the pedal lever  3  is disposed in its end position E. 
     The accelerator pedal module  1  has a restoring spring system  24 . The restoring spring system  24  has a first acting side  24   a  that engages the pedal lever  3  and a second acting side  24   b  that engages the spring-side linkage point  11   c  and the spring-side linkage point  12   c  of the two friction elements  11  and  12 . A spring linkage point  26  is provided on the pedal lever  3 . The spring linkage point  26  is embodied in the form of a blind bore and thus constitutes sufficient space for containing a part of the restoring spring system  24  and for guiding the restoring spring system  24 . The two blind bores of the spring linkage points  16  and  26  are essentially flush with each other. The restoring spring system  24  has the form of a helically wound compression spring. The restoring spring system  24  can also be comprised of several individual springs next to one another acting in parallel. The first acting side  24   a  is disposed inside the blind bore of the spring linkage point  26  and the second acting side  24   b  of the restoring spring system  24  is disposed inside the blind bore of the spring linkage point  16 . 
     The restoring spring system  24  presses the pedal lever  3  into its non-actuated starting position R. 
     By means of the crossbar  14  and by means of the spring-side linkage point  11   c , the second acting side  24   b  of the restoring spring system  24  presses the friction region  11   b  of the friction element  11  against the friction surface  21  provided on the pedal lever  3 . The support surface  18  of the support structure  2  secures the bottom linkage point  11   a  of the friction element  11  with a force which is essentially of the same magnitude as the force that the restoring spring system  24  exerts on the spring-side linkage point  11   c . The force acting on the friction element  11  via the bottom linkage point  11   a  vectorially added to the force acting via the spring-side linkage point  11   c  equals the force with which the friction region  11   b  of the friction element  11  is pressed against the friction surface  21  of the pedal lever  3 . The force with which the friction region  11   b  of the brake insert  10  presses against the friction surface  21  of the pedal lever  3  when the pedal lever  3  is actuated produces a friction force that opposes the movement of the pedal lever  3 . 
     FIG. 10 shows the actuation force F as a function of the adjustment path s. The actuation force F is the force acting on the pedal plate  3   a  during actuation of the pedal lever  3 . When the pedal lever  3  is actuated from the starting position R into the end position E, the actuation force F is significantly greater than the actuation force F that occurs when the pedal lever  3  is actuated from the actuated end position E back into the starting position R. In FIG. 10, the upper diagonal line shows the actuation force F when the pedal lever  3  is actuated from the starting position R into the end position E and the lower diagonal line shows the actuation force F when the pedal lever  3  is actuated from the actuated end position E into the starting position R. 
     Because the restoring spring system  24  is under less tension in the vicinity of the starting position R and because as a result, the force exerted by the restoring spring system  24  is less than the force exerted by the restoring spring system  24  when the pedal lever  3  is disposed in the actuated end position E, the friction force is less intense when the pedal lever  3  is disposed in the vicinity of the starting position R than when the pedal lever  3  is disposed in the vicinity of the end position E. This is also shown in FIG. 10 because, as can be inferred from FIG. 10, the distance between the upper diagonal line and the lower diagonal line is distinctly less in the vicinity of the starting position R than in the vicinity of the actuated end position E. This produces a desirable, particularly comfortable foot feel for the driver during actuation of the pedal lever  3 . 
     The brake insert  10  is embodied in the same way in the vicinity of the second friction element  12  as in the vicinity of the friction element  11  and the second friction element  12  acts on the pedal lever  3  in the same way as the friction element  11 . 
     A sensor  28  is connected to the support structure  2 . The sensor  28  has a sensor lever that is not shown. The movements of the sensor lever are coupled to the movements of the pedal lever  3 . Depending on the position of the sensor lever and pedal lever  3 , the sensor  28  sends an electrical signal to an electrical control unit that is not shown via an electrical line that is also not shown. The electrical control unit in turn controls, for example, a throttle valve that is not shown, which can be used to control the output of a driving engine. The sensor  28  and the pedal lever  3  are connected, for example, in the manner extensively described and depicted in WO 97/12780. 
     At least in its central region, i.e. in the vicinity of the friction region  11   b , the friction element  11  is quite flexible so that the friction region  11   b  adapts favorably to the friction surface  21  due to the force of the restoring spring system  24 . This offers the advantage that only very low demands have to be placed on the shaping precision and the concentricity of the friction surface  21 . In addition, only very low demands have to be placed on the manufacture and shaping precision of the friction element  11 . This has the advantage that the friction surfaces  21  and  22  can be manufactured at a very low cost. The friction elements  11  and  12  can also be produced very simply, with a very simple manufacturing process. As a result, the pedal lever  3  and also the brake insert  10  can be manufactured by means of an inexpensive process, for example by means of injection molding. No subsequent finishing work is required either for the friction surfaces  21  and  22  or for the friction elements  11  and  12 . 
     FIGS. 3,  4 ,  5 , and  6  show a second preferably selected, particularly advantageous exemplary embodiment. 
     FIG. 3 applies to both the first exemplary embodiment and the second exemplary embodiment. The cutting plane shown in FIG. 3 is also labeled III—III in FIG.  4 . FIG. 4 shows a longitudinal section through the accelerator pedal module  1 . The cutting plane shown in FIG. 4 is labeled I—I in FIG.  3  and is labeled IV—IV in FIG.  6 . FIG. 5 shows a detail of the brake insert  10  from the second exemplary embodiment. FIG. 6 shows a partial section through the brake pedal module  1 . The cutting plane and viewing direction shown in FIG. 6 is labeled VI—VI in FIG.  4 . 
     By contrast to the brake insert  10  shown in FIG. 2, the brake insert  10  of the second exemplary embodiment shown in FIG. 5 is not embodied of one piece, but rather the brake insert  10  is assembled by snapping together the friction element  11 , the second friction element  12 , and the crossbar  14 . 
     In the vicinity of the bottom linkage points  11   a  and  12   a , the brake insert  10  in the second exemplary embodiment is connected to the support structure  2  in the same way as in the first exemplary embodiment. 
     In the second exemplary embodiment, the crossbar  14  has a stepped through opening  14   a  and likewise stepped through opening  14   b . In the course of the through opening  14   a , there is a support surface  30 . The support surface  30  is oriented away from the pedal lever  3 . The spring-side linkage point  11   c  of the friction element  11  is hook-shaped. The linkage point  11   c  is dimensioned so that it can be pressed into the through opening  14   a  with a slight pressure. It is practically impossible to remove the spring-side linkage point  11   c  from the through opening  14   a  because the hook-shaped spring-side linkage point  11   c  is supported against the support surface  30  provided on the crossbar  14 . The second friction element  12  is connected to the crossbar  14  in the same manner as the friction element  11 . 
     The brake insert  10  can be assembled by simply snapping together the very easy-to-produce friction elements  11 ,  12  and the crossbar  14 . 
     FIG. 7 shows a partial section through a third preferably selected, particularly advantageous exemplary embodiment. 
     The cutting plane shown in FIG. 7 corresponds approximately to the cutting plane in the second exemplary embodiment shown in FIG.  6 . Details not shown in FIG. 7 essentially correspond to the details explained in conjunction with the first and second exemplary embodiments. 
     In the exemplary embodiment shown in FIG. 7, a coupling lever  33  is formed onto the support structure  2 . The coupling lever  33  can be produced along with the support structure  2  in a single mold by means of casting. 
     The coupling lever  33  is only connected to the support structure  2  in a very narrow region. This produces a one-piece, articulating connection  35  at the narrow region between the coupling lever  33  and the support structure  2 . The articulating connection  35  is disposed at one end of the coupling lever  33  and at the opposite end of the coupling lever  33 , the through opening  14   a  is provided in the coupling lever  33 . The connection  35  serves as a hinge between the coupling lever  33  and the support structure  2 . The spring-side of linkage point  11   c  of the friction element  11  is inserted into the through opening  14   a  of coupling lever  33 , as described in particular in conjunction with the second exemplary embodiment in FIG.  5 . 
     The spring linkage point  16  is provided on the coupling lever  33 . The restoring spring system  24  acts on the coupling lever  33  via the spring linkage point  16  and acts on the friction element  11  via the coupling lever  33  and the spring-side linkage point  11   c . As a result, in the third exemplary embodiment as well, the restoring spring system  24  presses the friction region  11   b  of the friction element  11  against the friction surface  21  provided on the pedal lever  3 . 
     In contrast to the first exemplary embodiment and the second exemplary embodiment, in the third exemplary embodiment, the second friction element  12  is eliminated. As a result, the third exemplary embodiment requires fewer components to be produced and assembled. 
     Because the second friction element  12  is eliminated in the third exemplary embodiment, the second friction surface  22  and the second projection  3   e  on the pedal lever  3  can also be eliminated. 
     FIG. 8 shows a fourth preferably selected, particularly advantageous exemplary embodiment. 
     In contrast to the exemplary embodiment shown in FIG. 7, in the exemplary embodiment shown in FIG. 8, the one-piece, articulating connection is not provided between the coupling lever  33  and the support structure  2 , but instead is disposed between the coupling lever  33  and the spring-side linkage point  11   c  of the friction element  11 . This offers the advantage that the friction element  11  and the coupling lever  33  can be produced together in a single mold by means of casting and/or injection molding. 
     At the end of the coupling lever  33  remote from the connection  35 , the coupling lever  33  is supported against the bottom  2   a  of the support structure  2  by means of a rocker bearing  37 . This assures that the force from the second acting side  24   b  of the restoring spring system  24  acting on the rocker arm  33  is transmitted by means of the rocker arm  33  and the one-piece, articulating connection  35  onto the friction element  11  and from the friction element  11  onto the friction surface  21  of the pedal lever  3 . 
     FIG. 9 shows a longitudinal section through a fifth preferably selected, particularly advantageous exemplary embodiment. 
     In the exemplary embodiments shown in FIGS. 1 to  8 , the brake insert  10  with the friction element  11  and possibly also with the second friction element  12  is associated with the support structure  2 . Correspondingly, the friction surface  21  is associated with the pedal lever  3 . When the pedal lever  3  is actuated, the friction elements  11 ,  12  of the brake insert  10  remain stationary and the friction surface  21  associated with the pedal lever  3  is moved along the stationary friction region  11   b ,  12   b  of the brake insert  10 . By contrast, in the exemplary embodiment shown in FIG. 9, the friction surface  21  and possibly the second friction surface  22  are associated with the support structure  2 . Consequently, the friction surface  21  and possibly the additional friction surface  22  remain stationary even when the pedal lever  3  is actuated. In the exemplary embodiment shown in FIG. 9, the brake insert  10  with the friction element  11  and possibly the additional friction element  12  is associated with the pedal lever  3 . When the pedal lever  3  is moved, the brake insert  10  with the friction element  11  and possibly the additional friction element  12  moves along with the pedal lever  3 . 
     In exemplary embodiment shown in FIG. 9, the first acting side  24   a  of the restoring spring system  24  presses against the stationary support structure  2  and the second acting side  24   b  of the restoring spring system  24  presses against the crossbar  14  of the brake insert  10  and consequently presses the friction region  11   b  of the friction element  11 , which moves when the pedal lever  3  in is actuated, against the stationary friction surface  21 . The second acting side  24   b  of the restoring spring system  24  acts on the pedal lever  3  by means of the crossbar  14 , the friction element  11 , and the linkage point  11   a  of the friction element  11  with the pedal lever  3 , and tries to move the pedal lever  3  into its starting position R. 
     In contrast to the exemplary embodiments shown in FIGS. 1 to  8 , in the exemplary embodiment shown in FIG. 9, the associations of the brake device  10  and therefore of the friction elements  11  and  12  and the friction surfaces  22  is reversed. More precisely stated, the brake device  10  with the friction element  11  and  12  is not associated with the support structure  2  but rather with the pedal lever  3 . And the friction surfaces  21  are not associated with the pedal lever  3 , but rather with the support structure  2 . All other details can be embodied in a correspondingly adapted manner, or alternatively in the same manner as in the exemplary embodiments explained in conjunction with FIGS. 1 to  8 . In order to avoid unnecessary repetition, please refer to FIGS. 1 to  8  with regard to details not shown in FIG.  9 . 
     In the selected exemplary embodiments shown in FIGS. 1 to  9 , the bearing pin  6  is supported in the housing bore  2   g  of the support structure  2  and in the bore  3   g  of the pedal lever  3 . However, it is also possible for the bearing pin  6  to be formed directly onto the pedal lever  3 , protruding laterally out from it. In this instance, the bore  3   g  is eliminated. On the other hand, is also possible to form the bearing pin  6  directly onto the support structure  2 . In this case, the housing bore  2   g  is eliminated. 
     In the exemplary embodiments shown in FIGS. 1 to  8 , the friction elements  11 ,  12  are clipped to the support structure  2  at the bottom linkage points  11   a ,  11   b . It is also possible for the friction elements  11 ,  12  to be formed in one piece onto the support structure  2  at the bottom linkage points  11   a ,  11   b . The same also applies to the exemplary embodiment shown in FIG.  9 . In this instance, for example, the friction element  11  can be formed in one piece onto the pedal lever  3  at its bottom linkage point  11   a.    
     The foregoing relates to preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.