Abstract:
In a hybrid vehicle system comprising an electric power storage system and an electric motor, the method includes a first step of allowing the electric power storage system to be discharged: upon detecting a condition of a charge of the electric power storage system that is greater than a first threshold to optimize power consumption; and upon detecting a condition of the charge of the electric power storage system that is greater than a second threshold to increase performance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a National Stage of International Application No. PCT/FR2009/051784, filed Sep. 22, 2009, which claims priority to French Application 0856410, filed Sep. 23, 2008. 
     
    
     FIELD 
       [0002]    The invention relates to a method and device for monitoring an energy storage system for hybrid vehicle comprising an electrical storage device and an electrical machine, e.g., an electric motor. The electrical storage system contributes to satisfying the demand for an energy boost needed to increase the performance of the vehicle, for instance during the acceleration phase of the vehicle, or to the optimization of the energy consumption of the vehicle, by supplying energy to the electrical machine which operates then in motor mode, reinforcing or replacing the torque of the combustion engine. 
       BACKGROUND 
       [0003]    Monitoring systems for energy storage systems of hybrid vehicles already exist. For instance, document U.S. Pat. No. 6,321,143 discloses a system for controlling electrical energy as a function of the use of the vehicle by defining several possible states of the vehicle and by adapting the energy use or the charge in these states. 
         [0004]    Document EP1410481 discloses a parallel system for managing the electrical energy of a hybrid vehicle which controls the power supply battery as a function of the demand and the parameters of the battery (e.g., temperature, charge state, etc). 
         [0005]    Document U.S. Pat. No,  6 , 223 , 106  discloses a control device for hybrid vehicle which manages the electrical energy. 
         [0006]    The prior art control methods and devices are not fully satisfactory. 
       SUMMARY 
       [0007]    To improve prior art control methods and devices, one objective of the invention is a method for controlling an energy storage system for a hybrid vehicle that includes an electrical storage device and an electrical machine. The method comprises a first stage arranged, i.e., operable, so that discharge of the storage device is authorized:
       upon detection of a state of charge of the storage device greater than a first threshold for optimization of the energy consumption of the vehicle; and   upon detection of a state of charge of the storage device greater than a second threshold for increasing the performance of the vehicle;       
 
         [0010]    In particular, the second threshold is established at a minimum energy value reserved for compensation of transitions. 
         [0011]    Advantageously, the first threshold delimits an energy range of variable height above the second threshold. 
         [0012]    One goal of the invention is also a device controlling an energy storage system for hybrid vehicle that includes an electrical storage device and an electrical machine. The device comprises:
       a first threshold arranged for authorizing the optimization of the energy consumption of the vehicle when the state of charge of the storage device is greater than the first threshold; and   a second threshold arranged, i.e., operable, for authorizing increased vehicle performance when the state of charge of the storage device is greater than the second threshold.       
 
         [0015]    In particular, the second threshold is fixed at a minimum energy value reserved for compensation of transitions. 
         [0016]    Advantageously, the first threshold delimits an energy range of variable height above the second threshold. 
     
    
     
       DRAWINGS 
         [0017]    The invention will be better understood by reading the following description and by examining the accompanying figures. The figures are provided only for illustration purposes and are not limiting the invention. 
           [0018]      FIG. 1  is a schematic representation of a plurality of essential elements of a hybrid vehicle for implementation of the invention; 
           [0019]      FIG. 2  is a flowchart showing the steps of a method for monitoring an energy storage system of the hybrid vehicle according to the invention. 
       
    
    
       [0020]    Identical elements retain the same indication from one figure to another. 
       DETAILED DESCRIPTION 
       [0021]    With reference to  FIG. 1 , a hybrid vehicle comprises an electric storage device  11  consisting of a battery, with super capacity or any other element suitable for storing in reversible manner electrical energy. Various electricity consuming devices  21  such as the head lights, the heating and air conditioning elements of the vehicle, the devices controlling the transmission, are connected to the terminals of the electrical storage device  11  and consume electrical energy which they need at the opportune time. A reversible converter  50  of electrical energy into mechanical energy consumes electrical energy supplied by the electrical storage device  11  in various situations. When a combustion engine supplies traction force to the vehicle, the electrical storage device  11  can supply an energy complement to improve performance, for instance in case of a request for more energy to accelerate the vehicle, which can be called “boost” according to the foreign language term with identical significance. The reversible converter  50  supplies energy to the electrical storage device  11  in particular when the vehicle decelerates or drives downhill, but this is not necessarily sufficient to ensure a zero energy balance. The reversible converter  50  must also supply electrical energy to recharge the electrical storage device  11  at other times when the combustion engine is running. 
         [0022]    One terminal  51  of the reversible converter  50  is connected with the positive pole of the electrical storage device  11  and the other terminal  52  is connected with the negative pole of the electrical storage device  11 . Between terminals  51  and  52 , the reversible converter  50  comprises for instance an electrical machine  53 , e.g., an electric motor, which supplies mechanical energy in motor mode when the reversible converter  50  is commanded by a signal element  41  and absorbs mechanical energy in generator mode to recharge the electrical storage device  11  when the reversible converter  50  is commanded by a signal  42 . Signals  41  and  42  are controlled by a module  40 , which is usually an electronic unit. Module  40  establishes the values of the signals  41  and  42  as a function of torque data supplied to the electrical machine  53  or absorbed by the electrical machine  53 . To this end, module  40  receives various commands, for instance from the braking units or acceleration units of the vehicle or from a module  30 , which is usually an electronic unit, which is arranged, i.e., operable, for receiving a charge level of the storage device  11  from a sensor  31 , which in a known manner measures the voltage at the terminals of the electrical storage device  11  and estimates its impedance starting from the electrical current passing through the electrical storage device  11 . More in particular, module  40  receives a control command signal  61  from a module  60 , which is usually an electronic module. Module  60  is arranged, i.e., operable, for authorizing in a controlled manner a discharge of the storage device  11 . As we shall see in the following description, signal  61  contains an instruction regarding the energy or power to be consumed by the reversible converter  50  starting from storage device  11 , following a request for complementary energy received through a signal  63 , in order to increase the performance of the vehicle or following a request for useable energy, received through a signal  62 , for optimizing the energy consumption of the vehicle. 
         [0023]    A performance increase, for instance when accelerating, consists in general of adding the torque of the electrical machine  53  to the torque of the combustion engine in order to increase the acceleration of the vehicle. Optimization of the energy consumption of the vehicle, for instance at low traveling speed, consists in general of using mainly the torque of the electrical machine  53  and turning off the combustion engine so that fuel consumption of the vehicle is reduced. 
         [0024]    Module  60  is arranged, i.e., operable, for instance by means of a microprocessor and a digital or analog memory, for executing the method explained here with reference to  FIG. 2 . 
         [0025]    With reference to  FIG. 2 , the control method comprises a first stage  806  arranged so that discharge of the storage device  21  is authorized when one of the three following transitions is validated. 
         [0026]    A transition  805  is validated upon detection of a state of charge (SOC) of the storage device  11  greater than a first threshold Lv, which is the low limit of the green energy range, especially dimensioned to optimize the energy consumption of the vehicle, for instance at low cruising speed or during city driving. 
         [0027]    A transition  811  is validated upon detection of a state of charge of the storage device greater than a second threshold Lr, which is the lower limit of the orange energy range, especially dimensioned to increase the performance of the vehicle, for instance when accelerating. 
         [0028]    A transition  813  is validated by a request for energy to compensate transitions. The validation of this transition is not necessarily linked to logic detection but can result naturally from a transitional phenomenon. The second threshold Lr is also the high limit of the minimum red energy range especially dimensioned so that the energy quantity is rapidly repaid in case of reduction, through direct recharging of the storage device  11  via the combustion engine or through recuperation during a weak deceleration. 
         [0029]    The value of Lr determines the guaranteed minimum dynamic performance of the vehicle. 
         [0030]    The sustainability of the vehicle&#39;s energy rests on energy which is not accessible by the consumption optimization strategy, the priority recharge relative to the green range, the decanting of the consumption optimization energy when it is available and a quantity of energy which by design is easily repaid. To this end, the second threshold is fixed at a minimum energy value reserved for compensation of transitions. 
         [0031]    The first threshold, which is the low limit of the green range, is also the high limit of the orange range. By making the threshold parametric or a function of the lifetime conditions of the vehicle, the first threshold will delimit an energy range with variable height above the second threshold. 
         [0032]    The transition  805  is validated following a stage  802  which measures the level or the state of charge of the storage device  11  SOC (State Of Charge) when a request for consumption optimization validates a transition  801 . 
         [0033]    A transition  803  is validated following stage  802  when the level or the state of charge SOC of the storage device  11  is smaller than or equal to threshold Lv, so that a stage  804  is activated which interdicts then the discharge of the storage device  11  to optimize the energy consumption of the vehicle. 
         [0034]    The transition  811  is validated following a stage  808  which measures the level or state of charge of the storage device  11  SOC when a request for increased performance validates a transition  807 . 
         [0035]    A transition  809  is validated following stage  808  when the level or the state of charge of the storage device  11  SOC is smaller than or equal to a threshold Lr, so that a stage  810  is activated which interdicts then the discharge of the storage device  11  to increase the performance of the vehicle. 
         [0036]    To implement the method, a device for controlling an energy storage system for the hybrid vehicle that includes the electrical storage device  11 , the electrical machine  53  and the module  60 , comprises for instance in digital or analog memory (not shown):
       the first threshold Lv, wherein the device is arranged, or operable, to authorize the optimization of the energy consumption of the vehicle when the state of charge of the storage device  11  is greater than the first threshold Lv; and   the second threshold Lr, wherein the device is arranged, or operable, for authorizing increased vehicle performance when the state of charge of the storage device  11  is greater than the second threshold Lr.       
 
         [0039]    The second threshold Lr is by preference fixed at a minimum energy value reserved for compensation of transitions. 
         [0040]    The first threshold Lv is by preference variable, delimiting an energy range of variable height above the second threshold Lr.