Abstract:
A motor vehicle including an electric drive engine capable of being successively supplied with electric power by two separate electric power sources, in particular by a set of batteries and by a fuel cell, and of the type including an accelerator pedal that is mobile between a rest position and an extreme actuated position corresponding to the maximum power capable of being supplied by the engine based on the amount of electric power available for its powering. A mechanism is provided for varying the extreme actuated position of the pedal on the basis of a parameter representing the amount of electric power available for powering the engine.

Description:
The invention relates to a motor vehicle provided with an electric propulsion motor capable of being supplied with electrical energy by two distinct energy sources. 
   The invention relates more particularly to a motor vehicle provided with an electric propulsion motor capable of being supplied with electrical energy:
         by a first electrical-energy source composed of a fuel-cell stack that is supplied with fuel by a reformer when the temperature of the reformer is higher than or equal to a threshold temperature; or   by a second electrical-energy source composed of an auxiliary battery, as long as the temperature of the reformer is below the threshold temperature;   and of the type provided with an accelerator pedal that can be moved between a rest position and an actuated extreme position corresponding to the maximum mechanical power that can be delivered by the motor as a function of the electric power available for supplying it.       

   Vehicles powered by an electric motor can be advantageously supplied with electrical energy by a fuel-cell stack. 
   A fuel-cell stack is composed mainly of two electrodes, an anode and a cathode, which are separated by an electrolyte. This type of cell stack permits direct conversion, to electrical energy, of the energy produced by the following oxidation-reduction reactions:
         a reaction of oxidation of a fuel or “carburant”, which continuously supplies the anode; and   a reaction of reduction of an oxygen carrier, which continuously supplies the cathode.       

   BACKGROUND OF THE INVENTION 
   The fuel-cell stacks used to supply electrical energy on board motor vehicles are generally of the solid-electrolyte type, especially with a polymeric electrolyte. Such a cell stack uses especially hydrogen (H 2 ) and oxygen (O 2 ) as the fuel and oxygen carrier respectively. 
   With this type of cell stack, it is possible to achieve, at the same time, an efficiency, a reaction time and an operating temperature that on the whole are satisfactory for delivering electricity to an electric motor for propulsion of a motor vehicle. 
   In contrast to combustion engines, which discharge a non-negligible quantity of polluting substances with the exhaust gases, the fuel-cell stack offers in particular the advantage of discharging only water, which is produced by the reduction reaction at the cathode. In addition, the oxygen carrier of a cell stack of the type described in the foregoing can be ambient air, the oxygen (O 2 ) of which becomes reduced. 
   The cathode generally has an inlet that permits continuous supply with oxygen (O 2 ) or with air, and an outlet that permits evacuation of the excess air or oxygen (O 2 ) as well as evacuation of the water produced during the reduction of oxygen (O 2 ). In general, the anode is generally provided with an inlet through which hydrogen (H 2 ) is introduced. 
   In the current state of the art, however, the storage of pure hydrogen (H 2 ) on board the vehicle necessitates a volume that is too large to achieve comfortable autonomy. In addition, the logistics of distribution of hydrogen (H 2 ) have not yet become geographically widespread. 
   It is known that these problems can be overcome by producing hydrogen (H 2 ) directly on board the vehicle from hydrocarbons, especially conventional fuels such as gasoline or natural gas. The hydrogen (H 2 ) is extracted from the gasoline during an operation known as reforming, which necessitates a device known as a reformer. 
   The gasoline is injected into the reformer together with water and air. The product of reforming is a gas known as reformate, which is composed mainly of hydrogen (H 2 ), carbon monoxide (CO), carbon dioxide (CO 2 ), oxygen (O 2 ) and nitrogen (N 2 ). The anode of the cell stack is then supplied directly with reformate by the reformer. 
   To be able to produce such a reformate, the reformer must be heated and maintained at a temperature higher than a threshold temperature. For this purpose, the reformer is provided with a heating device. Below this threshold temperature, the reformer cannot supply the cell stack with hydrogen (H 2 ) fuel, and the cell stack therefore cannot produce electrical energy. 
   However, the threshold temperature of the reformer is higher than the ambient temperature to which the vehicle is likely to be exposed. Thus, when the reformer is cold, the heating device needs a non-negligible time, which can be as much as several minutes, to bring it to temperature. During this time, the electric motor cannot be supplied by the fuel-cell stack, and the operator must wait until the reformer is operating before he can use the motor vehicle. 
   To permit the operator to use the vehicle quickly after it has been started, it is known that the vehicle can be equipped with a battery of auxiliary accumulators in order to supply the electric motor during the time for heating the reformer. Thus, during heating of the reformer, the motor is supplied with electrical energy by the auxiliary battery and, when the reformer has reached its threshold temperature, the electrical-energy supply source automatically switches from the battery to the fuel-cell stack. 
   However, such a battery generally cannot deliver as much electrical power to the motor as a fuel-cell stack. This has consequences for the maximum power that the motor can deliver instantaneously and thus for the driving sensations of the operator. 
   To permit the operator to control the electric motor, the vehicle is generally provided with an accelerator pedal, which can be moved between a rest position and a maximum position, which corresponds to the maximum power that can be delivered by the motor as a function of the electrical power that can be released by the fuel-cell stack. The pedal is also capable of occupying a threshold position, which is situated between the rest position and the actuated maximum position, and which corresponds to the maximum power that can be delivered by the motor when it is being supplied by the battery. 
   When the motor is being supplied by the battery, the actuation of the accelerator pedal from the rest position to the threshold position is felt as a continuous increase of power by the operator. The actuation of the accelerator pedal beyond the threshold position then has no effect on the power delivered by the motor, contrary to what the operator expects when the motor is being supplied normally by the fuel-cell stack. 
   In addition, when the supply source of the motor changes over automatically from the auxiliary battery to the fuel-cell stack, and when the accelerator pedal is actuated beyond the threshold position, the motor is suddenly supplied by a greater electrical power. The abrupt increase of power delivered by the motor as a consequence is then capable of surprising the operator and/or of causing an accident. 
   U.S. Pat. No. 6,447,939 B1 describes a device in which, when a “quick down” is detected during startup of the reforming phase, the quantity of electrical energy necessary for startup of the reformer is limited and the quantity of electrical energy distributed to the motor is increased by giving priority to the supply of the motor. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to provide an improved motor vehicle equipped with means for varying the actuated extreme position of the accelerator pedal. 
   The present invention proposes a vehicle of the type described in the foregoing, characterized in that it is provided with means for varying the actuated extreme position of the pedal as a function of a parameter representative of the electrical power available to supply the motor. 
   According to other characteristics of the invention:
         the said representative parameter is the temperature of the reformer;   when the temperature of the reformer is higher than the threshold temperature, the said means automatically vary the actuated extreme position of the accelerator pedal between a threshold position corresponding to the electrical power that can be released by the battery and a maximum position corresponding to the electrical power that can be delivered by the fuel-cell stack;   the said means that vary the actuated extreme position of the pedal are controlled by the action of the operator;   the said means are controlled by the action of the operator via a manual control device, which is neutralized as long as the temperature of the reformer is below the threshold temperature;   the said means vary the actuated extreme position of the pedal when the accelerator pedal is situated between the rest position and an intermediate position that is situated between the rest position and the threshold position;   the said means automatically vary the actuated extreme position of the pedal after a delay time;   the vehicle is provided with means for increasing the resistance to displacement of the accelerator pedal from the threshold position to the maximum position, the said means being actuated automatically and temporarily;   the vehicle is provided with a warning device that transmits a warning signal to alert the operator when the temperature of the reformer is higher than the threshold temperature;   the said means are provided with a retractable stop, which can be moved between an active state in which the displacements of the accelerator pedal are limited between the rest position and the threshold position, and an inactive state in which the pedal is able to reach the maximum position.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
     Other characteristics and advantages of the invention will become apparent by reading the detailed description hereinafter, which will be understood by referring to the attached drawings, wherein: 
       FIG. 1  schematically represents a motor vehicle designed according to the teachings of the invention; 
       FIG. 2  is a view of the accelerator pedal of the vehicle represented in  FIG. 1 , equipped with a device for varying its actuated extreme position according to the teachings of the invention; 
       FIG. 3  is a sectional view of the pedal and of the device in section plane  3 — 3  of  FIG. 2 ; 
       FIG. 4  is a diagram illustrating the functioning of the vehicle represented in  FIG. 1 ; 
       FIG. 5  represents the pedal of  FIG. 2 , in this case equipped with an alternative version of the device for varying its actuated extreme position; 
       FIG. 6   a  is a sectional view in section plane  6 — 6  of  FIG. 5 , representative of the device in an active state; 
       FIG. 6   b  is a view analogous to that of  FIG. 6   a , representative of the device in semi-active state; 
       FIG. 6   c  is a view analogous to that of  FIG. 6   b , representative of the pedal actuated beyond a threshold position; 
       FIG. 6   d  is a view analogous to that of  FIG. 6   a , representative of the device in its inactive state. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
   In the description hereinafter, there will be adopted, on a non-limitative basis, a longitudinal, vertical and transverse orientation indicated by the coordinate system L, V, T of  FIG. 2 . 
     FIG. 1  schematically represents a motor vehicle  10  provided with an electrical propulsion motor  12 . Vehicle  10  is also provided with an auxiliary battery  14  and a fuel-cell stack  16 , which in this case are capable of supplying motor  12  successively with electrical energy. 
   The electrical supply circuit of motor  12 , which is represented by fine continuous lines, is provided with a selector switch  18 , which is intended to select the electrical-energy supply source of motor  12 . 
   Thus selector switch  18  can occupy a primary position  18   a , in which fuel-cell stack  16  supplies motor  12  with electrical energy, or an auxiliary position  18   b , in which battery  14  supplies motor  12  with electrical energy. In this case an inverter  20  is integrated into the electrical supply circuit between switch  18  and motor  12 . 
   Fuel-cell stack  16  has already been described in the introduction. It is supplied with an oxygen carrier, which in this case is oxygen O 2 , and with fuel, which in this case is hydrogen H 2 , via a supply circuit, which is represented in bold continuous lines in  FIG. 1 . 
   The cell stack is supplied with oxygen carrier by an air-compression device  21 . 
   Fuel-cell stack  16  is supplied with fuel by a reformer  22 , which extracts hydrogen H 2  from a hydrocarbon such as gasoline. The hydrogen that supplies reformer  22  is contained in a tank  24 . 
   To be able to function, reformer  22  must be heated and maintained at a temperature higher than a threshold temperature Ts. To this end, reformer  22  is equipped with a heating device (not illustrated). 
   As has already been explained in the introduction, the threshold temperature Ts of reformer  22  is higher than the ambient temperature to which vehicle  10  is likely to be exposed. Thus, when the operator starts vehicle  10  from cold condition, a non-negligible time for heating of reformer  22 , which can be as long as several minutes, is necessary to bring reformer  22  up to its threshold temperature Ts. 
   Reformer  22  is therefore provided with a temperature sensor  26 , which transmits a signal representative of the temperature Tm of reformer  22  to an electronic control unit  28 . The exchange lines over which signals are received or transmitted by electronic control unit  28  are represented by broken lines in  FIG. 1 . 
   After it has received the measurement Tm of the temperature of reformer  22 , electronic control unit  28  compares the measured temperature Tm of reformer  22  with the threshold temperature Ts:
         if the temperature Tm of reformer  22  is lower than the threshold temperature Ts, electronic control unit  28  selects auxiliary position  18   b  of switch  18 ;   if the temperature Tm of reformer  22  is higher than the threshold temperature Ts, electronic control unit  28  selects primary position  18   a  of switch  18 .       

   The passenger compartment (not illustrated) of vehicle  10  is provided in this case with an accelerator pedal  30 , which is mounted pivotally between a rest position P 0  corresponding to zero power delivered by motor  12  and a maximum position P 2  corresponding to the maximum power delivered by motor  12  when it is being supplied by fuel-cell stack  16 . Thus pedal  30  permits the operator to control the power delivered by motor  12 , for example in a manner proportional to the angular travel of accelerator pedal  30 . 
   Pedal  30  can also occupy a threshold position P 1 , which is situated between rest position P 0  and maximum position P 2 . Threshold position P 1  corresponds to the power that motor  12  can deliver when it is being supplied by auxiliary battery  14 . In other words, when motor  12  is being supplied by auxiliary battery  14 , the power delivered by motor  12  remains constant beyond this threshold position P 1 . 
   The functional principle of pedal  30  is as follows. 
   A position sensor  32  of pedal  30  transmits a signal representative of the angular position of pedal  30  to an electronic control unit  28 . Electronic control unit  28  then transmits a signal destined for inverter  20 , so that the said inverter “orders”, from the selected electrical energy source  14  or  16 , the electrical power necessary for motor  12  to deliver the required mechanical power. 
   In the rest of the description, we will call actuated extreme position of pedal  30  the position to which the operator can depress pedal  30  before reaching the stop. 
   According to the teachings of the invention, vehicle  10  is provided with a device  34  for varying the actuated extreme position of pedal  30  and in particular for limiting the displacements of pedal  30  between rest position P 0  and maximum position P 2 , or between rest position P 0  and threshold position P 1 . 
   We will now describe pedal  30  equipped with this device  34  by referring to  FIGS. 2 and 3 . 
   Pedal  30  is composed mainly of a crank  36 , vertical overall, at the lower end of which there is mounted a pad  38  intended to receive a force applied by the foot of the Operator. The upper end of crank  36  is mounted to rotate relative to the vehicle structure, around a transverse axis A. 
   According to this embodiment of the invention, the upper end of the crank is provided with a head  40 , in which there is formed a substantially longitudinal, oblong groove  42 . Front end  44  of groove  42  is intended to cooperate with a retractable stop  46 , which is integral with the structure of vehicle  10 , in order to limit the displacements of pedal  30  between rest position P 0  and threshold position P 1 . 
   Retractable stop  46  is mounted to slide transversely in a box  48 , which is integral with the structure of vehicle  10  and is mounted close to head  40  of pedal  30 . 
   Retractable stop  46  is controlled by an electromagnet  50  mounted in the interior of box  48 . By means of electromagnet  50 , electronic control unit  28  controls stop  46 , in particular between:
         an active state (represented in  FIG. 3 ), in which stop  46  is able to cooperate with front end face  44  of groove  42  in order to limit displacements of pedal  30  between its rest position P 0  and its threshold position P 1 , threshold position P 1  then being the actuated extreme position of pedal  30 ; and   an inactive state (not illustrated), in which stop  46  is retracted by sliding transversely to the right according to  FIG. 3 , in such a way as to permit displacements of pedal  30  between its rest position P 0  and its maximum position P 2 , maximum position P 2  then being the actuated extreme position.       

   We will now describe the functioning of vehicle  10  by referring to the diagram of  FIG. 4 . 
   During a first step E 1 , the operator starts vehicle  10 , then during a second step E 2 , temperature sensor  26  delivers the temperature Tm of reformer  22  to electronic control unit  28 . Electronic control unit  28  then compares the temperature Tm of reformer  22  with the threshold temperature Ts. 
   If the temperature Tm of reformer  22  is lower than the threshold temperature Ts, then electronic control unit  28  initiates a limitation step E 3 , in the course of which it selects auxiliary position  18   b  of switch  18  in such a way that motor  12  is supplied by auxiliary battery  14 . 
   During step E 3 , and after selection of switch  18  in auxiliary position  18   b , electronic control unit  28  activates retractable stop  46  in such a way that the extreme actuated position of pedal  30  corresponds to threshold position P 1 . 
   Thus, when the operator actuates accelerator pedal  30 , the latter is displaced freely between rest position P 0  and threshold position P 1 , groove  42  being traveled freely by stop  46 . 
   When the operator actuates pedal  30  as far as threshold position P 1 , front end face  44  of groove  42  abuts against retractable stop  46 , and pedal  30  is then in actuated extreme position. 
   When the temperature Tm of reformer  22  is higher than or equal to the threshold temperature Ts, electronic control unit  28  initiates an operator-warning step E 4 , in the course of which the operator is alerted by means (not illustrated), for example by turning on an indicator light on the control panel of the vehicle, or by an acoustic signal, that an energy source of greater capacity than auxiliary battery  14  is available, or in other words that fuel-cell stack  16  is available. 
   Step E 4  is followed by a release step E 5 , in the course of which electronic control unit  28  causes switch  18  to assume primary position  18   a , so that fuel-cell stack  16  supplies electric motor  12 . 
   Then, when switch  18  is in primary position  18   a , electronic control unit  28  selects the inactive state of retractable stop  46 , so that the actuated extreme position of pedal  30  corresponds to its maximum position P 2 . Pedal  30  can then be displaced freely between its rest position P 0  and its maximum position P 2 . 
   According to another embodiment of the invention, during release step E 5 , electronic control unit  28  selects the inactive state of retractable stop  46  only after a time delay, for example of several seconds, after the indicator light goes on. Alerted by the indicator light, the operator thus has time to become aware that the actuated extreme position of pedal  30  will be modified and as a result he is less likely to depress accelerator pedal  30  involuntarily. 
   According to another embodiment of the invention, during release step E 5 , the transition of retractable stop  46  to the inactive state is brought about not only as a function of the temperature Tm of reformer  22  but also as a function of the position of accelerator pedal  30 . Thus retractable stop  46  is moved to the inactive state only when:
         the temperature Tm of reformer  22  is higher than or equal to the threshold temperature Ts;   and when pedal  30  is situated between its rest position P 0  and an intermediate position P 1 ′, which is situated on the low side of threshold position P 1 .       

   Thus, when motor  12  is being supplied by auxiliary battery  14  and the operator is maintaining his pressure on pedal  30  so as to lock it in its actuated extreme position (or in other words its threshold position P 1 ), during the transition of switch  18  from auxiliary position  18   b  to primary position  18   a , the operator must necessarily relax his pressure on pedal  30  to allow the latter to move to intermediate position P 1 ′, before he is able once again to displace the pedal between its threshold position P 1  and its maximum position P 2 . 
   In this way, even if the operator does not notice the indicator light, he cannot depress accelerator pedal  30  involuntarily beyond threshold position P 1 . 
   In another alternative embodiment of the invention, during step E 5 , electronic control unit  28  controls a manual intermediate device (not illustrated) for tripping retractable stop  46 , which is situated in the passenger compartment of vehicle  10 . 
   As long as the temperature Tm of reformer  22  is lower than the threshold temperature Ts, the operator is unable to act on the manual tripping device, because the latter is inhibited or neutralized by electronic control unit  28 . 
   When the temperature Tm of reformer  22  is higher than or equal to the threshold temperature Ts, electronic control unit  28  activates the manual tripping device. Thus, then the operator is alerted by the fact that the indicator light goes on, he himself manually trips the device, which initiates the transition of retractable stop  46  to the inactive state. 
   The manual tripping device is, for example, a pushbutton connected electrically to electronic control unit  28 . 
   According to another embodiment of the invention, stop  46  is temporarily able to occupy a semi-active state, which is intended to be tripped during release step E 5  and in which the displacements of pedal  30  between its threshold position P 1  and its maximum position P 2  require that the operator apply on pad  38  a pressure greater than the pressure required when stop  46  is inactive. 
   This embodiment relies on an alternative version  52  of device  34  for varying the actuated extreme position of the pedal represented in  FIGS. 2 and 3 . This alternative version is represented in  FIGS. 5 ,  6   a ,  6   b ,  6   c  and  6   d.    
   We will now describe the structural differences between this device  52  and the previously described device  34 . 
   In this case retractable stop  46  is provided with a transverse tin  54  which is intended to cooperate with a stop shoulder  55  integral with the box when stop  46  is in active state, in such a way that stop  46  is fixed relative to box  48  when front end face  44  of the pedal is brought into contact with stop  46 . 
   Box  48  is perforated by a substantially longitudinal opening  56  intended to guide stop  46  in longitudinal sliding manner when the said stop is in a semi-active state in which stop  46  can move relative to box  48 , and when pedal  30  is being displaced between its threshold position P 1  and its maximum position P 2 . 
   Box  48  is also provided with a compression spring  58 , the orientation of which is longitudinal on the whole relative to the orientation of  FIG. 2 , and on which spring stop  46  is braced. Spring  58  is intended in particular to exert an additional force opposing the pressure that the operator applies on pedal  30  when the stop is in semi-active position. In addition, spring  58  makes it possible to retract stop  46  elastically to the longitudinal position that it occupies in the active or inactive state. 
   Box  48  is provided with an electromagnet  50 , which controls a transverse rod  60  provided with a notch  62 , which is intended to receive a longitudinal dog point carried by stop  46  to permit transverse displacement of stop  46 . 
   We will now describe the functioning of device  52  with reference to  FIGS. 6   a ,  6   b ,  6   c  and  6   d.    
     FIG. 6   a  represents device  52  in the active state. Stop  46  is then engaged in groove  42 , and it is immobilized as regards longitudinal translation relative to box  48  by stop shoulder  55 , which blocks dog point  54 . The displacements of pedal  30  are then limited between rest position P 0  and threshold position P 1 . 
     FIGS. 6   b  and  6   c  show device  52  in the semi-active state. Electromagnet  50  then acts on rod  60 , which undergoes a first transverse translation to the right according to the orientation of  FIG. 6   b , rod  60  and stop  46  being made integral by nesting of dog point  64  in notch  62 . Thus stop  46  is also displaced transversely to the right in such a way that stop  46  is always engaged in notch  42  and in such a way that lug  54  is no longer adjacent to stop shoulder  55 . 
   Thus, as illustrated in  FIG. 6   b , when the operator actuates the pedal beyond its threshold position P 1 , front end face  44  of pedal  30  transmits the pressure of pedal  30  to stop  46 . Since the latter is no longer blocked longitudinally by stop shoulder  55 , it is free to be displaced into opening  56  of box  48 . The longitudinal displacement of stop  46  compresses spring  58 , which then exerts an opposing force on stop  46  and therefore on pedal  30 . 
   When pedal  30  is returned to its threshold position P 1 , dog point  64  once again becomes engaged in notch  62  of rod  60 . Device  52  can then be inactivated, as illustrated in  FIG. 6   d . Electromagnet  50  acts on rod  60  in such a way that the latter undergoes a second transverse translation to the right. Rod  60  therefore carries stop  46  in transverse translation to the right according to  FIG. 6   d  in such a way that stop  46  is completely disengaged from groove  42 . Pedal  30  is then capable of being displaced between its rest position P 0  and its maximum position P 2 . 
   According to this embodiment, when the temperature Tm of reformer  22  is higher than or equal to the threshold temperature Ts, electronic control unit  28  temporarily selects the semi-active stage of stop  46 . The operator therefore has the feeling that he can actuate pedal  30  beyond its threshold position P 1 , but he must make a conscious effort to overcome the resistance of spring  58 . 
   A few seconds after the transition of stop  46  to-the semi-active state, electronic control unit  28  causes stop  46  to change over to the inactive state, and so the operator has had the opportunity to become aware of the increase of power that motor  12  can deliver. 
   It will be understood that simple mechanical inversions can constitute alternative embodiments of the invention.