Abstract:
An accelerator pedal unit is known comprising an accelerator pedal, an actuator, and a control shaft via which the actuator can transmit a restoring torque to the accelerator pedal. The accelerator pedal unit can generate an additional restoring force which acts on the accelerator pedal, for example in order to regulate or limit the speed of a vehicle or to function as a warning device in the event of speeding. In the accelerator pedal unit according to the invention, the actuator is mechanically decoupled from the accelerator pedal. According to the invention, the torque of the control shaft ( 3 ) is transmitted to the accelerator pedal ( 1 ) via a damping element ( 10 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an accelerator pedal unit comprising an accelerator pedal, an actuator and a control shaft via which the actuator can transmit a restoring torque to the accelerator pedal. 
     An accelerator pedal unit is already known from the German patent publication DE 10 2009 021 585 A1, comprising an accelerator pedal, an actuator and a control shaft, by means of which a restoring torque can be transmitted to the accelerator pedal. The accelerator pedal unit can generate an additional restoring force which acts on the accelerator pedal, for example in order to regulate or limit the speed of a vehicle or to function as a warning device in the event of speeding. Disadvantageously, the actuator and the accelerator pedal are rigidly coupled to each other. As a result, brief losses of torque of the actuator, for example losses of torque of a brushed DC electric motor (torque ripple), are transmitted to the accelerator pedal with no change in their relative magnitude and are noticeable to the driver in a disruptive manner. A further disadvantage is that the additional restoring force generated by the actuator is subject to uncontrollable fluctuations due to different effects. Firstly, an undesirable increase in the restoring force can occur due to inertia forces as a result of coupled co-movement of the actuator during a quick actuation of the accelerator pedal. Secondly, the mechanical gearing mechanism path is afflicted with friction, so that the force actually transmitted to the accelerator pedal is dependent on temperature. Moreover, the relationship between the generated engine torque and the current applied to the actuator is subject to unpredictable fluctuations which are dependent on temperature and material and component tolerances. 
     SUMMARY OF THE INVENTION 
     The accelerator pedal unit according to the invention has in contrast the advantage that the actuator is mechanically decoupled from the accelerator pedal by the torque of the control shaft being transmitted via a damping element to said accelerator pedal. From a mechanical perspective, a spring or damping element is thus disposed between the control shaft and the accelerator pedal. Torque fluctuations of the actuator which occur are damped to a great extent by the damping element, so that said fluctuations are unnoticeable to the driver. 
     According to one advantageous embodiment, the damping element is designed as a helical spring, torsion spring, flexible spring or rubber spring. 
     It is particularly advantageous if a control lever for transmitting the torque is provided on the control shaft, wherein the damping element is connected at one end to the control lever and at the other end to the control shaft. 
     It is furthermore advantageous for the control lever to be rotatably mounted on the control shaft because the restoring torque is transmitted in this way exclusively via the dampening element. 
     It is very advantageous for the damping element to be attached with the end thereof associated with the control shaft to a shoulder connected to said control shaft because the damping element can be attached particularly easily to said control shaft in this way. 
     It is also advantageous for the damping element to extend around the control shaft with at least one winding because the damping element can thereby be disposed in a very space saving manner. 
     It is furthermore advantageous for the control lever to comprise a rotatably mounted rolling element because the torque can be transmitted with little friction from the control lever to the accelerator pedal in this way. 
     In addition, it is advantageous for the control lever to act on a surface of the accelerator pedal which is provided with a coating because the torque can be transmitted in this way form the control lever to the accelerator pedal in a practically frictionless and low-noise manner. 
     It is advantageous for a positioning spring to be provided which is attached with the one end thereof to a rotationally fixed housing section and acts with the other end on the control lever. The positioning spring ensures a bracing of a gearing mechanism disposed between the actuator and the accelerator pedal independently of the effective direction thereof; thus enabling the tooth flanks of the teeth of the gearing mechanism to fit tightly against each other. In so doing, there is little noise during the operation of the gearing mechanism. 
     In addition, it is advantageous for the positioning spring to be designed in such a manner that said spring pushes the control lever towards the accelerator pedal or in the opposite direction into a stop position that is spaced apart from the accelerator pedal. According to the first alternative, the positioning spring acts as a restoring spring against the spring force of the damping element. According to the second alternative, the positioning spring acts in the direction of the damping element and ensures that the control lever is constantly in contact with the accelerator pedal, whereby the actuator can very quickly introduce a force into the accelerator pedal. 
     It is furthermore advantageous for the damping element and the positioning spring to each be provided on a bearing bushing that is rotationally mounted on the control shaft. In this way, it is ensured that the springs are well guided and cannot break out in an undefined manner when subjected to a mechanical load. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is depicted in a simplified manner in the drawings and is explained in detail in the following description. In the drawings: 
         FIG. 1  shows an accelerator pedal unit according to the invention in a three dimensional view. 
         FIG. 2  shows a top view of the inventive accelerator pedal unit according to  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an accelerator pedal according to the invention in a three dimensional view. 
     The accelerator pedal unit according to the invention comprises a rotatably mounted accelerator pedal  1 , an actuator  2  and a control shaft  3  via which the actuator  2  can transmit a restoring torque to the accelerator pedal  1 . In this way, the accelerator pedal unit can take on functions, such as, for example, actively limiting the speed of a vehicle or indicating that the speed limit is being exceeded. 
     The accelerator pedal  1  is mounted so as to be rotatable about a rotational axis  4  and has a first lever arm  5  which can be actuated by foot and a second lever arm  6  which can be actuated by means of the actuator  2 . The first lever arm  5  and the second lever arm  6  lie on opposite sides in relation to the rotational axis  4 . The actuator  2  is, for example, a direct current motor, DC motor or brushless motor. 
     The control shaft  3  is rotatably mounted, for example in at least one pivot bearing. 
     Provision is made according to the invention for the torque of the control shaft  3  to be transmitted via a damping element  10  to the accelerator pedal  1 . In this way, the control shaft  3  exerts a predefined restoring force on the accelerator pedal  1  when current is passed through the actuator  2 . The damping element  10  is designed as a helical spring according to the exemplary embodiment, can, however, also be a torsion spring, flexible spring or rubber spring. When designed as a helical spring, the damping element  10  extends around control shaft  3  with at least one winding and is therefore disposed and supported on the control shaft  3 . According to the exemplary embodiment, the damping element  10  has a spring stiffness in a range between 30 Nmm/degree and 80 Nmm/degree. In the case of a helical spring, the damping element  10  extends helically or in a thread-like manner around the control shaft. 
     A control lever  11  which transmits the torque to the accelerator pedal  1  is provided on the control shaft  3 , wherein the damping element  10  is connected at one end to the control lever  11  and at the other end to the control shaft  3 . According to the exemplary embodiment, the damping element  10  is connected to the control shaft  3  at the other end. The control lever  11  is arranged on the control shaft  3  in a rotatably mounted manner, for example by the control shaft  3  protruding through an opening in the control lever. In this way, it is ensured that the torque is transmitted exclusively via the damping element  10  and not directly from the control shaft  3  to the accelerator pedal  1 . 
     The damping element  10  is inserted with the end thereof associated with the control lever  11 , for example, into an opening of the control lever  11  or is hooked into a receiving area. With the end thereof associated with the control shaft  3 , the damping element  10  is, for example, attached to a shoulder  12  that is connected to the control shaft  3  in a rotationally fixed manner or, respectively, to a control arm  12  that is connected to said control shaft  3  in a rotationally fixed manner. According to the exemplary embodiment, the shoulder or, respectively, the control arm  12  is a separate, disk-shaped or plate-shaped component which is attached on the control shaft  3  in a rotationally fixed manner, for example in a positive locking and force-fitting manner. Of course, the shoulder can, however, also be connected to the control shaft  3  in a materially bonded manner. The shoulder  12  can also be omitted, and the dampening element  10  can be directly attached to the control shaft  3 . The damping element  10  is, for example, inserted into an opening  13  of the shoulder  12  with the end thereof facing said shoulder  12  or is hooked into a receiving area. A rotatably mounted rolling element  16  can be provided on the control lever  11 , said rolling element acting on a surface of the second lever arm  6  of the accelerator pedal  1 . The surface  17  can be provided with a predefined coating in order to reduce the friction between said surface  17  of the accelerator pedal  1  and the rolling element  16  of the control lever  11 . 
     A positioning spring  20  can be provided which is attached with the one end thereof to a rotationally fixed housing section  21  and acts with the other end thereof on the control lever  11 . The positioning spring  20  is arranged, for example, like the damping element  10  on the control shaft  3  and is designed, for example, as a helical spring or as a spiral spring. The positioning spring  20  extends helically or in a thread-like manner around the control shaft  3  in the case of a helical spring and spirally in the case of a spiral spring. The spiral spring requires very little installation space in the axial direction with respect to the control shaft  3 . An unspecified noise and/or vibration dampening element can be provided on the positioning spring  20  which fits snugly against said positioning spring  20 . 
     The housing section  21  is, for example, formed by a so-called bearing bracket with which the accelerator pedal unit is attached to a vehicle. The positioning spring  20  can be designed in such a manner that said spring pushes the control lever  11  either towards the accelerator pedal  1  or in the opposite direction into a stop position that is spaced apart from said accelerator pedal  1 . According to the first alternative, the positioning spring  20  acts as a restoring spring against the spring force of the damping element  10 . According to the second alternative, the positioning spring  10  acts in the direction of the damping element  10  and ensures that the control lever  11  is constantly in contact with the accelerator pedal  1 , whereby the actuator  2  can very quickly introduce a force into the accelerator pedal  1 . In both cases, the positioning spring  20  is installed with an elastic preload. The positioning spring  20  is, for example, inserted with the one end thereof into an opening of the housing section  21  and, for example, loosely rests under preload with the other end thereof against the control lever  11 . 
     The damping element  10  and the positioning spring  20  can each be disposed on a bearing bushing  22  that is rotatably mounted on the control shaft  3 . The bearing bushing of the positioning spring  20  can also be integrally formed with the control lever  11 . The bearing bushing  22  can also in each case be omitted and the diameter of the control shaft  3  can be designed in such a manner that said control shaft  3  itself takes on the guidance and support of the springs  10 ,  20 . 
     In addition, a gearing mechanism  24  can be provided between the actuator  2  and the control shaft  3 , said gearing mechanism transmitting the rotational movement of the actuator  2  with a predefined speed reduction. The positioning spring ensures a bracing of the gearing mechanism  24  independently of the effective direction thereof; thus preventing a tooth flank change in the gearing mechanism  24 . In so doing, there is little noise during the operation of the gearing mechanism. 
     The gearing mechanism  24  is, for example, a spur gear unit or a worm gear, wherein the worm gear can be of self-locking or non-self-locking design. The damping element is designed in such a manner that the accelerator pedal  1  can still be moved at least by 5 degrees in the event of a blockage of the gearing mechanism. This enables an emergency operation of the vehicle. The damping element  10  is thus not allowed to go solid within these at least 5 degrees. When the accelerator pedal is actuated while the gearing mechanism  24  is blocked, a torque is exerted by the accelerator pedal  1  on the damping element  10  so that said element is deformed. 
       FIG. 2  shows a view from above onto the inventive accelerator pedal unit according to  FIG. 1 . 
     In the accelerator pedal unit according to  FIG. 2 , the parts which remain the same or act the same with respect to the accelerator pedal unit according to  FIG. 1  are denoted with the same reference signs. 
     The actuator  2  and the gearing mechanism  24  are disposed according to the exemplary embodiment on the side of the housing section  21  that faces away from the accelerator pedal  1 , wherein the control shaft  3  protrudes via a through-hole through the housing section  21 . Provision is, for example, made for the control shaft  3  to be rotationally mounted in the through-hole.