Abstract:
A gas-pedal module has a gas pedal ( 12 ) which is mounted pivotably in a housing and can be actuated, counter to a restoring spring, with pedal-force-dependent hysteresis, a pedal-position sensor producing an electric signal corresponding to the pedal position. In view of the high pedal forces, precise and expensive bearings are necessary in order to avoid jamming of the gas pedal ( 12 ). In order to reduce the production costs arid nevertheless reliably to prevent jamming, it is proposed to mount the gas pedal ( 12 ) in a floating manner in a bearing element ( 28 ) which has play in the upward direction. Specific selection of the coefficient of friction on the contact surface ( 30 ) between the bearing journal ( 18 ) and the bearing element ( 28 ) makes it possible to achieve a hysteresis as is desired in the case of such gas-pedal modules.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a gas-pedal module having a gas pedal which is mounted in a housing and can be actuated, counter to the force of a restoring spring, with pedal-force-dependent hysteresis, and having a pedal-position sensor which produces an electric signal corresponding to the pedal position. 
     In gas pedals for motor vehicles, use is being made increasingly frequently of so-called “drive-by-wire” systems, in the case of which the gas pedal is no longer connected to the throttle via a Bowden wire, as has been the case up until now, but rather a sensor produces an electric output signal which corresponds to the gas-pedal position and passes, via lines, to an engine control system, which activates the throttle via an electric actuating motor in dependence on the signals. 
     From the Bowden wires which have usually been used up until now, the vehicle drivers are accustomed, during actuation of the gas pedal, to a force hysteresis which is derived from the frictional forces acting in the Bowden wire. These frictional forces set an increased resistance against the pressing-down action of the pedal and, when a certain gas-pedal position is being held, relieve the driver&#39;s foot of the restoring forces of the restoring spring. The counter pressure, when the gas pedal is pressed down, allows more precise positioning of the gas pedal, while the foot being relieved when a gas-pedal position is being held improves comfort. 
     With the “drive-by-wire” systems, attempts were made to maintain these desirable characteristics of the gas pedal, for which purpose a simulation of the properties of a Bowden wire with its restoring spring was necessary. 
     In order to simulate the hysteresis, use is usually made of direction-dependent frictional elements, as are outlined, for example, in DE 195 17 172. This document also discloses the conventional play-free mounting of the gas pedal in a housing. Since the mounting of the gas-pedal lever, on the one hand, has to be precise but also, at the same time, has to absorb very high pedal forces, a particularly high-quality, play-free mounting (for example needle bearings) has to be provided in order to avoid the possible occurrence of jamming. The costs of such a gas-pedal module are thus considerable. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is to provide a gas-pedal module which can absorb high pedal forces and nevertheless does not involve the risk of the gas pedal jamming. 
     The object is achieved according to the invention in that the gas pedal is mounted in a floating manner in a bearing element which has play in the upward direction. 
     The bearing element, which is at least half-open, allows precise mounting of the gas pedal on the one hand and on the other hand, by virtue of the possibility of yielding in the upward direction, reliably prevents possible jamming of the gas pedal in its bearing location. In this case, a very small allowance for movement is sufficient in order to eliminate the risk of jamming reliably. 
     The solution according to the invention manages with extremely simple bearing elements, for example in the form of a half-shell. 
     The spring element is preferably a helical spring which, via a lever arm, produces a restoring moment which is directed counter to the moment provided by the actuating force about the pivot axis of the gas pedal. In this case, the force which is produced by the helical spring is preferably directed essentially counter to the bearing force of the gas pedal in the bearing element. 
     Consequently, both the actuating force and the restoring force of the spring are supported in the bearing element, this resulting in an increased friction moment when the pedal is pressed down, and thus in a certain hysteresis. 
     In order to achieve certain hysteresis characteristics, it is advantageous if the contact surface between the bearing element and a circumferential surface of the gas pedal is designed as a friction pairing with a certain coefficient of friction. 
     Such a configuration of the bearing element and of the mounted surface of the gas pedal makes it possible to achieve a hysteresis of the desired magnitude without separate components being used. In comparison with conventional designs with rockers, spring elements, frictional elements and damping elements, the mounting of which involves very high outlay in part, this constitutes a considerably simplification in design, which allows the production costs of gas-pedal modules to be reduced further without the mechanical properties being compromised. 
     It is also possible for the contact surface between the bearing element and the circumferential surface of the gas pedal to be subdivided into two circumferential-segment regions, which form two radial supporting locations. It is particularly advantageous here if at least one radial supporting location can be adjusted in the circumferential direction in relation to the circumferential surface of the gas pedal. This allows the characteristics of the gas-pedal module to be changed simply by adjusting a supporting location. This makes it possible to achieve simple adaptation of the frictional hysteresis, to a respective vehicle type, which corresponds to the character and the image of the vehicle. The development of a single gas-pedal module with a pedal housing and optimum friction-lining pairing is sufficient here, which makes a considerable contribution to the reduction of development costs. The force hysteresis is determined here from the following factors: coefficient of friction, geometry and normal force. 
     The gas-pedal travel is preferably limited in an idling position by a first stop and in the full-load position by a second stop. The travel between these two precisely defined positions can be initiated in a desired manner by the gas-pedal sensor and transmitted to the engine electronics. 
     Furthermore, in the case of vehicles with automatic transmission, it is desirable to provide a kick down position for the gas pedal. 
     For a gas-pedal module according to the invention, this may be realized such that, in the case of further-increased pedal pressure in the full-throttle position, the second stop forms a second pivot axis of the gas pedal, the gas pedal lifting off from the bearing element and passing into a kick down position. The changed pivot axis of the gas pedal results in a characteristic signal deviation of the gas-pedal sensor, it being possible for said signal deviation to be clearly assigned to the kick down position. 
     The level of the change in force which is necessary for achieving the kick down position can be defined in a customer-specific manner such that the second stop, for defining the necessary pedal pressure, is arranged at a certain distance from the bearing element. A third stop expediently serves for limiting the gas-pedal travel in the kick down position. 
     For pedal-position sensors, use is made nowadays of usually series-produced potentiometers with a slider fixed on the axis of rotation of the pedal arm. With the floating mounting of the gas pedal, this may result in difficulties in certain circumstances since radial movements of the slider on the housing-mounted resistive tracks may result in a signal deviation which cannot be distinguished from a rotary movement. The problem may be eliminated, for example, in that, instead of the potentiometers which have been customary up until now, use is made of sensors which operate with magneto resistive action and react exclusively to the orientation of the magnetic field and thus do not generate any signal deviations in the case of radial movements. 
     It is also possible for the gas-pedal module according to the invention to operate with potentiometers. For this purpose, it is provided that at least one potentiometer is mounted separately from the gas pedal and can be actuated via elements with play compensation separately in mechanical terms from the gas pedal. The play compensation for mechanical separation is necessary in order to compensate for any possible displacements of the gas pedal in relation to the bearing location. The play compensation may be achieved, for example, in that provided on the potentiometer is a lever arm which butts, under an abutment force provided by a compression spring, against a curved contour on the gas pedal. It is also possible for the lever arm to be guided in a guide slot in the gas pedal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is discussed in more detail hereinbelow using exemplary embodiments and with reference to the attached drawings, in which: 
     FIG. 1 shows a schematic cross section of a gas-pedal module in the idling position; 
     FIG. 2 shows the gas-pedal module according to FIG. 1 in the full-load position; 
     FIG. 3 shows the gas-pedal module according to FIGS. 1 and 2 in the kick down position; 
     FIG. 4 shows a cross section of a further embodiment of a gas-pedal module in the idling position; 
     FIG. 5 shows the gas-pedal module according to FIG. 4 in a section which has been rotated through 90°; and 
     FIG. 6 shows a cross section of a further embodiment of a gas-pedal module in the idling position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a schematic illustration of a gas-pedal module  10  which usually has a housing (not illustrated), similarly to the variants described in FIGS. 4 to  6 . 
     The gas-pedal module  10  has a gas pedal  12  which comprises a pedal lever  14  with a pedal surface  16 , a bearing journal  18  and a second lever arm  20 . A prestressed compression spring  22 , which is supported on a housing-mounted abutment  24 , acts from above on the second lever arm, which is integrally formed horizontally on the bearing journal  18  opposite the pedal lever  14 . In this way, the compression spring  22  produces a restoring moment, which counteracts the actuating moment provided by pressure on the pedal surface  16 . 
     The bearing journal  18  has a circumferential surface  26  which is supported in a bearing element  28  which, in the region of an actual contact surface  30  between the circumferential surface  26  and the bearing element  28 , is adapted to the contour of the circumferential surface  26 . The bearing element  28  is of open configuration in the upward direction, with the result that the bearing journal  18  has a certain amount of play in the upward direction, this being limited by a stop  32 . The contact surface  30  is designed as a friction pairing with a certain coefficient of friction, with the result that it is possible to dispense with additional frictional elements necessary for achieving an actuation-dependent force hysteresis. The travel of the pedal lever  14  is limited in the idling position by a first, idling stop  34 , which absorbs the restoring moment produced by the compression spring  22  in the idling position of the pedal  12 . The bearing force of the bearing journal  18  is determined here from the pre-stressing force of the compression spring  22  and the leverage between the point at which the idling stop  34  acts with the contact surface  30  and the point at which the compression spring  22  acts on the second lever arm  20 . 
     If, then, a corresponding pressure is exerted on the pedal surface  16 , the gas pedal passes, via the partial-load range, into a full-load position, which is illustrated in FIG.  2  and is limited by a full-load stop  36 . On account of the contoured contact surface  30 , the bearing journal  18  rotates about its center axis  38  in this case without displacement in a radial direction taking place. 
     When the driver steps on the gas pedal  12 , the frictional forces occurring in the contact surface  30  set a resistance against the actuation, this resistance improving the pedal feel, but nevertheless making it easier to hold the pedal  12  in position when the latter is static. 
     In the case of automatic transmissions, it is desired to provide a so-called kick down position beyond the normal full-throttle position of the gas pedal  12 , said kick down position causing shifting down of the transmission. Up until now, it has been customary to provide additional switches which can be initiated by the gas pedal  12 . In the case of the above described gas-pedal module  10 , however, it is possible to realize a kick down position without such additional elements. In this case, the full-throttle stop  36  serves as a movable bearing for the pedal lever  14 , about which the entire gas pedal  12  pivots when the pedal pressure is increased beyond the full-throttle position. By virtue of the gas pedal  12  pivoting about the full-throttle stop  36 , the bearing journal  18  lifts off from the bearing element  28 , the compression spring  22  being compressed further in the process, and the travel of said bearing journal is limited by the stop  32 . The level of the change in force which is necessary for achieving the kick down position can be adapted in a customer-specific manner by variation in the length of the active lever arm between the bearing point of the full-load stop  36  and the bearing location  28 . The change in the axis of rotation of the gas pedal  12  also results in a characteristic signal deviation of a pedal-position sensor coupled to the gas pedal  12  (see, for example, FIGS.  4  and  5 ), with the result that, upon achieving the kick down position, the vehicle electrics can give rise to the corresponding engine and transmission functions. 
     Once the gas pedal  12  has been released, the compression spring  22  first of all presses the bearing journal back into the contoured contact surface  30  and then ensures that the gas pedal is pivoted back into the idling position about the center axis  38  of the bearing journal  18 . On account of the bearing element  28  being constructed to be open in the upward direction, this reliably prevents jamming at the bearing location since the bearing journal can execute extremely small yielding movements, which result in an immediate drop in the frictional forces acting in the contact surface. 
     It may be expedient, for the floating mounting of the bearing journal  18  in the bearing element  28 , to use magneto resistive sensors for sensing the pedal position, said sensors reacting merely to the orientation of the magnetic field and not reacting with undefined changes in signal in the case of the bearing journal  18  being displaced in the radial direction. If, however, it is desired to use the hitherto conventional potentiometers as pedal-position sensors, a gas-pedal module  40  corresponding to the design illustrated in FIGS. 4 and 5 is recommended. The gas-pedal module  40  is illustrated with a housing  42  which has an opening  44  through which a gas pedal  46  runs into the housing interior. In this case, the top edge  48  of the opening  44  forms the idling stop, while the bottom edge  50  forms the full-load stop. A compression spring  52 , which is arranged with pre-stressing between a lever arm  54 , which is connected to the gas pedal  46 , and the housing, ensures the restoring action of the gas pedal  46 . 
     The gas pedal  46  has two bearing journals  56  which are integrally formed laterally and are mounted in bearing locations  58  in the side walls of the housing  42 . Although the bearing locations  58  are closed on all sides, it is only the bottom region of their contact surfaces  60  which is designed in accordance with the contour of the bearing journal  56 . In the upward direction, the bearing locations have a clearance  62 , the top edge  64  of the bearing location  58  forming the stop for the kick down position. 
     The pedal-position sensor provided for this embodiment is a potentiometer  66 , of which the resistive tracks are arranged on a housing wall. The slider  68  is arranged on a pivot lever  70 , which is mounted in an essentially play-free manner on a separate shaft  72  in the housing  42 . The pivot lever  70  butts against a curved contour  74  on the gas pedal  46 , with the result that, in accordance with the configuration of the curved contour  74 , pivoting of the gas pedal  46  results in pivoting of the pivot lever  70  and thus in an adjustment of the potentiometer  66 . The pivot lever  70  pivots counter to the restoring moment of a torsion spring  76 , which is arranged between the housing  42  and the bearing shaft  72  of the pivot lever  70 . It is also conceivable to have slot guidance of the pivot lever  70  in a suitable cutout in the gas pedal  46 . 
     As has already been described above, the frictional forces occurring on the contact surfaces  30 ,  60  ensure a desired pedal-force-dependent hysteresis. The frictional force can be influenced in a specific manner by varying the bearing-journal diameter and the friction pairing on the contact surfaces  30 ,  60 . 
     FIG. 6 illustrates a further gas-pedal module  80  which, despite a preselected diameter of the bearing journal  82  of the gas pedal  84  and a preselected friction pairing on the contact surfaces  86  of bearing locations  88 , allows the frictional force to be influenced in a specific manner. The gas-pedal module  80  otherwise corresponds to the gas-pedal module  10 , which is illustrated in FIGS. 1 to  3 . 
     In contrast to the above described gas-pedal modules  10 ,  40 , the gas-pedal module  80 , which is shown in FIG. 6, has two bearing locations  88  arranged at different locations of the circumference of the bearing journal  82 . Said bearing locations are arranged adjustably in the circumferential direction, with the result that it is possible to adjust to a certain extent the points at which the radial supporting forces for the bearing journal  82  act. By varying the points at which the forces act, it is possible to change the lever geometry such that the resulting normal force, which is a direct measure of the frictional forces occurring, can be varied. The bearing locations  88  simply comprise in this case friction linings  90 , which are optimized in terms of their wear and frictional behavior. This means that one type of gas-pedal modules can be adapted to a wide range of different vehicle types. 
     Since, in all cases, the frictional force is merely determined from the leverage, the coefficient of friction of the friction pairings and the normal forces of the bearings, wear of the friction linings does not result in any significant change in the actuating characteristics of the gas pedals  12 ,  46 ,  84 . 
     The above described modules  10 ,  40 ,  80  can be used, in principle, not just in conjunction with gas pedals of motor vehicles but in all “drive-by-wire” systems in which a hysteresis of the actuating force is to be simulated, for example, for simulation of the frictional behavior of Bowden wires which have been used up until now.