CONTROL OF CHARGES BY RECOVERY OF BRAKING TORQUE OF A CELLULAR BATTERY OF A LAND VEHICLE

Abstract

A method for controlling the recharges of a cellular battery fitted to a land vehicle comprising an electric prime mover, coupled to this cellular battery and capable of recovering braking torque when the driver completely stops pressing the accelerator pedal. This method comprises a step (10-30) in which, in the event of ceasing to press the accelerator pedal, a braking torque of a first chosen value is recovered with the prime mover for a first chosen duration, then this recovered braking torque is gradually reduced for a second chosen duration to a second chosen value, then the recovery of braking torque is continued at this second value. Figure 3

Description

Title of the invention: CONTROL OF RECHARGES BY RECOVERY OF BRAKING TORQUE OF A CELLULAR BATTERY OF A LAND VEHICLE Technical field of the invention

[0001] The invention relates to land vehicles comprising a cellular battery associated with a rechargeable electric motor, and more precisely to the control of recharging by recovery of braking torque from such cellular batteries. State of the art

[0002] Certain land vehicles (possibly of the automobile type) comprise a powertrain (or GMP) comprising at least one electric motor associated with a rechargeable cellular battery and capable of recovering braking torque when the driver completely stops pressing the accelerator pedal and at the same time the current state of charge of the cellular battery allows it.

[0003] Here, the term “cellular battery” means a battery comprising at least one electrochemical cell, for example of the lithium-ion (or Li-ion) or Ni-Mh or Ni-Cd type.

[0004] Braking torque recovery causes the (land) vehicle to decelerate by regenerative (or regenerative) braking, without the driver needing to press the brake pedal. Of course, if the driver feels he needs more braking power than that provided by regenerative braking, he can press the brake pedal to supplement the latter.

[0005] Generally, the value of the recovered braking torque is fixed. For example, it can be chosen so as to induce a deceleration of 2 m.s2. Sometimes, the vehicle can have at least two regenerative braking modes associated respectively with different recovered braking torque values, from which the driver can make a choice. However, the colder the outside temperature, the more the recharging capacity of the cellular battery is reduced, and therefore the more the value of the braking torque setpoint is reduced by an on-board computer, such as for example the GMP supervision computer or the braking system computer, which results in a reduction in the intensity of the deceleration provided by the regenerative braking.

[0006] As is known to those skilled in the art, during recharging of a cellular battery by recovery of braking torque, the voltage at the terminals of this cellular battery can be subject to oscillations which can induce an accumulation effect of a chemical species around the anode (or "plating") which constitutes a metallic deposit which can cause a short circuit or overheating that could trigger a fire in the event of thermal runaway. Generally, this metallic deposit begins to form when the recharging power that supplies the cellular battery comes from a braking torque that is greater than a predefined value for a predefined duration.

[0007] In order to combat the formation of the metallic deposit, certain GMP or braking system supervision computers implement a strategy consisting of starting to recover a braking torque, having the maximum value permitted by the current state of charge and the outside temperature, for a duration almost equal to the aforementioned predefined duration, then reducing by one decrement the value of the braking torque recovered for a certain duration in order to prevent the formation of the metallic deposit, before starting again to recover a braking torque having the maximum value permitted by the current state of charge and the outside temperature.

[0008] A main disadvantage of this strategy lies in the fact that the lower the temperature, the lower the maximum value of the recovered braking torque permitted by the current state of charge, and therefore the more the reduction in braking power induced by the reduction by the decrement of the value of the recovered braking torque is felt by the driver of the vehicle, without him understanding the reason. Consequently, the driver will first be surprised by the weakness of the initial regenerative braking resulting from the maximum value established, then surprised again by the sudden reduction in regenerative braking induced by the decrement, which may not only prove dangerous but also make the driver dissatisfied, or even worried, about the operation of the regenerative braking of his vehicle.

[0009] The invention therefore aims in particular to improve the situation. Presentation of the invention

[0010] It proposes in particular for this purpose a control method intended to allow control of recharging of a cellular battery equipping a land vehicle comprising an electric motor, coupled to its cellular battery and capable of recovering braking torque when a driver completely stops pressing an accelerator pedal.

[0011] This control method is characterized by the fact that it comprises a step in which, in the event of cessation of pressure on the accelerator pedal, a braking torque of a first chosen value is recovered with the prime mover for a first chosen duration, then the recovered braking torque is progressively reduced for a second chosen duration to a second chosen value, then the recovery of braking torque is continued at this second value.

[0012] Thanks to the invention, it is now possible to significantly limit, or even prevent, the formation of metallic deposits in the cells, while greatly reducing, or even eliminating, the surprise effect of the driver, which prevents the driver from being dissatisfied, or even worried, about the operation of the regenerative braking of his vehicle.

[0013] The control method according to the invention may include other characteristics which may be taken separately or in combination, and in particular:

[0014] - in its step, the progressive reduction can be done according to a gradient included between 3% of the first value per second and 15% of the first value per second;

[0015] - in the presence of the first option, in its stage, the progressive reduction can be do according to a gradient which is between 5% of the first value per second and 10% of the first value per second;

[0016] - in its step, the first and second values ​​can be chosen according to of a current state of charge of the cellular battery;

[0017] - in the presence of the last option, in its step, the first and second values can be chosen further depending on a temperature outside the cellular battery and / or a regenerative braking mode chosen from at least two modes;

[0018] - in its step, the first and second durations can be chosen so that their sum is less than or equal to a third duration beyond which the cellular battery begins to be subject to a metallic deposit on at least one anode of a cell which it comprises, in the presence of a recharging power, supplying the cellular battery, resulting from a braking torque greater than the second value.

[0019] The invention also provides a computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing a control method of the type presented above, in a land vehicle comprising a cellular battery and an electric motor, coupled to this cellular battery and capable of recovering braking torque when a driver completely stops pressing an accelerator pedal, to control recharging of the cellular battery by recovery of braking torque by the motor.

[0020] The invention also proposes a control device intended to control recharges of a cellular battery equipping a land vehicle comprising an electric motor, coupled to its cellular battery and capable of recovering braking torque when a driver completely stops pressing an accelerator pedal.

[0021] This control device is characterized by the fact that it comprises at least one processor and at least one memory arranged to carry out the operations consisting, in the event of cessation of pressure on the accelerator pedal, in triggering a recovery by the driving machine of a braking torque of a first value chosen during a first chosen duration, then a progressive reduction for a second chosen duration of the recovered braking torque down to a second chosen value, then triggering a continuation of the braking torque recovery at this second value.

[0022] The invention also proposes a land vehicle, possibly of the automobile type, and comprising, on the one hand, a cellular battery and an electric motor, coupled to this cellular battery and capable of recovering braking torque when a driver completely stops pressing an accelerator pedal, and, on the other hand, a control device of the type presented above. Brief description of the figures

[0023] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0024] [Fig. 1] schematically and functionally illustrates an example of the embodiment of a land vehicle comprising a control device according to the invention and a GMP with an electric motor coupled to a cellular battery,

[0025] [Fig.2] schematically and functionally illustrates an example of the embodiment of a supervision calculator comprising a control device according to the invention,

[0026] [Fig.3] schematically illustrates an example of an algorithm implementing a control method according to the invention, and

[0027] [Fig.4] schematically illustrates an example of a time evolution diagram of the recharging power of a cellular battery during recharging by braking torque recovery carried out by implementing the control method according to the invention. Detailed description of the invention

[0028] The invention aims in particular to propose a control method, and an associated DC control device, intended to allow the control of the recharging of a cellular battery BC equipping a land vehicle V by recovery of braking torque by an electric motor MME of the latter (V).

[0029] In the following, it is considered, by way of non-limiting example, that the land vehicle V is of the automobile type. It is for example a car, as illustrated in [Fig.l]. But the invention is not limited to this type of land vehicle. It relates in fact to any type of land vehicle comprising a powertrain (or GMP) comprising at least one electric motor associated with a rechargeable cellular battery and capable of recovering braking torque when the driver completely stops pressing the accelerator pedal.

[0030] Furthermore, it is considered in the following, by way of non-limiting example, that the land vehicle V includes a powertrain (or GMP) transmission chain of the all-electric type (and therefore comprising at least one electric motor associated with a cellular battery). But the GMP could be of the hybrid type (and in this case the drive of land vehicle V is provided by at least one thermal motor and one electric motor).

[0031] [Fig.l] schematically shows a (land) vehicle V (here a car) comprising an all-electric GMP transmission chain (and therefore comprising at least one electric MME motor machine), a supervision computer CS, a service battery BS, a cellular battery BC associated with a battery computer CB, a converter CV, and a DC control device according to the invention.

[0032] The service battery BS is responsible for supplying electrical energy to the on-board network RB of the (land) vehicle V, in addition to that supplied by the converter CV powered by the cellular battery BC via a main electrical circuit, and sometimes instead of this converter CV. For example, this service battery BS can be arranged in the form of a very low voltage type battery (typically 12 V, 24 V or 48 V). It is rechargeable at least by the converter CV. It is considered in the following, by way of non-limiting example, that the service battery BS is of the 12 V Lithium-ion type.

[0033] The on-board network RB is an electrical power supply network to which electrical (or electronic) equipment (or components) that consume electrical energy are coupled.

[0034] The main electrical circuit (or "high voltage" or "power") is connected, on the one hand, to the cellular battery BC via an interface device, and, on the other hand, to electronic equipment, such as for example the converter CV and the driving machine MME. It also allows the external recharging of the cellular battery BC by an external power source and temporarily coupled to the vehicle V for example via a recharging connector CN of the latter (V).

[0035] The transmission chain has a GMP which is, here, purely electric, and therefore which comprises, in particular, in addition to its (electric) driving machine MME, a motor shaft, and a transmission shaft. Here, the term "electric driving machine" means an electric machine arranged so as to provide torque to move the vehicle V, as well as to recover braking torque to brake the vehicle V (instead of or in addition to its braking system (not shown)) and recharge the cellular battery BC. The operation of the GMP is supervised by a supervision computer CS.

[0036] The driving machine MME (here an electric motor) is coupled to the cellular battery BC via the main electrical circuit, in order to be supplied with energy electric and to supply this cellular battery BC with electrical energy during a regenerative braking phase. It is coupled to the motor shaft, to provide it with torque by rotating it. This motor shaft is here coupled to a reducer RD which is also coupled to the transmission shaft, itself coupled to a first train Tl (here of wheels), preferably via a differential DF.

[0037] This first train T1 is here located in the front part PVV of the vehicle V. But in a variant this first train T1 could be the one which is here referenced T2 and which is located in the rear part PRV of the vehicle V.

[0038] The operation of the driving machine MME is controlled by a machine computer CM, and supervised by the supervision computer CS.

[0039] As indicated above, the prime mover MME is capable, in a regenerative braking phase, of recovering braking torque whose value is defined by a regenerative braking torque setpoint. This recovered braking torque is converted by the prime mover MME into recharging current which supplies the cellular battery BC to recharge it. The regenerative braking torque setpoint is determined, for example, by the supervision computer CS or the braking system computer, when the driver completely stops pressing the accelerator pedal PA of the vehicle V and at the same time the current state of charge ece of the cellular battery BC allows it (i.e. if it is not already too high).

[0040] It will be understood that this recovery of braking torque causes a deceleration of the vehicle V by regenerative braking, without the driver needing to press the brake pedal PF of the vehicle V. The intensity (or value) of this deceleration is a function of the regenerative braking torque setpoint. If the driver considers that he needs braking power greater than that offered by regenerative braking, he can press the brake pedal PF to supplement the latter.

[0041] It will be noted that the vehicle V may possibly have at least two regenerative braking modes associated respectively with different values ​​of recovered braking torque and therefore with different deceleration intensities. In this case, the driver can make a choice among these modes.

[0042] The CV converter is also responsible, here, during the driving phases of the vehicle V for converting part of the electric current stored in the cellular battery BC to supply converted electric current to the on-board network RB and the service battery BS (to recharge it). It is also, here, electrically coupled, via the main electrical circuit, to the charging connector CN of the vehicle V. During an external charging phase of the cellular battery BC, this charging connector CN is, here, intended to be temporarily coupled to a power source external to the vehicle V, via a charging cable.

[0043] It will be noted, as illustrated non-limitingly in [Fig.l], that the converter CV can be part of an internal charger CH responsible, at least, for controlling the recharges of the cellular battery BC.

[0044] The cell battery BC comprises at least one cell CE, and preferably several. For example, each cell CE may be electrochemical, possibly of the lithium-ion (or Li-ion) or Ni-Mh or Ni-Cd type. Also for example, the cell battery BC may be of the low voltage type (typically 450 V for illustration). But it could be of the medium voltage or high voltage type.

[0045] It will be noted, as illustrated non-limitingly in [Fig. 1], that when the cellular battery BC comprises several cells CE, they can be distributed in modules MC which are coupled together, for example in series. Here, the term “module MC” means a group of at least one cell CE. When an MC module comprises several cells CE, the latter (CE) can be coupled together in series and / or in parallel.

[0046] It will also be noted that the cellular battery BC is associated with a battery box BB which notably comprises means for measuring voltage, current and internal temperature (not illustrated) and a battery calculator CB. This battery calculator CB centralizes the current measurements, the voltage measurements and the internal temperature measurements (notably those which individually concern each of the N cells CE), and estimates parameters of the cellular battery BC as a function of these measurements, and notably its internal resistance, its minimum voltage, its charge, and its current state of charge (or SOC) ece.

[0047] It will also be noted that in the example illustrated non-limitingly in [Fig.l] the vehicle V also comprises a distribution box BD to which the service battery BS, the converter CV and the on-board network RB are coupled. This distribution box BD is responsible for distributing in the on-board network RB the electrical energy which is produced by the converter CV or stored in the service battery BS, for the supply of the electrical components (or equipment) coupled to the on-board network RB, according to power supply requests received (in particular from the supervision computer CS of the GMP).

[0048] As mentioned above, the invention proposes in particular a control method intended to allow the control of the recharges of the cellular battery BC during the regenerative braking phases, and therefore each time the driver suddenly stops pressing the accelerator pedal PA.

[0049] This (control) method can be implemented at least partially by the DC control device (illustrated in [Fig.2]) which comprises for this purpose at least one processor PR1, for example a digital signal processor (or DSP (“Digital Signal Processor "), and at least one MD memory. This DC control device can therefore be implemented in the form of a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software"). For example, it can be a microcontroller.

[0050] The memory MD is RAM in order to store instructions for the implementation by the processor PR1 of at least part of the control method. The processor PR1 may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is understood to mean any type of device capable of carrying out at least one electrical or electronic operation.

[0051] In the example illustrated non-limitingly in Figures 1 and 2, the control device DC is part of the supervision computer CS. But it could be part of another computer on board the vehicle V (such as for example the braking system computer), or could comprise its own dedicated computer.

[0052] As illustrated non-limitingly in [Fig.2], the (control) method, according to the invention, comprises a step 10-30 which is implemented each time the driver suddenly stops pressing the accelerator pedal PA, and therefore a regenerative braking phase must begin.

[0053] Step 10-30 of the method comprises a sub-step 10 in which, in the event of cessation of pressure on the accelerator pedal PA, a braking torque of a first value vl is recovered with (for example the control device DC triggers the recovery by) the driving machine MME for a first chosen duration dl. It will be understood that this first value vl is defined by a first regenerative braking torque setpoint and that it induces a first intensity (or value) idl of deceleration of the vehicle V and a first recharging power prl of the cellular battery BC.

[0054] Step 10-30 of the method then comprises a sub-step 20 in which the recovered braking torque is progressively reduced (for example the DC control device triggers a progressive reduction), for a second chosen duration d2, until a second chosen value v2 is reached (with v2 < vl). In other words, the value of the recovered braking torque is progressively varied so that it gradually passes from the first value vl to the second value v2 (strictly lower (in absolute value) than the first value vl). It will be noted that in reality the value of a regenerative braking torque setpoint is always negative and therefore the first value vl is lower than the second value v2, but the absolute value of the first value vl is greater than the absolute value of the second value v2.

[0055] Step 10-30 of the method then comprises a sub-step 30 in which continues (for example the DC control device triggers the continuation of) the braking torque recovery at the second value v2. In other words, a braking torque whose value is equal to the second value v2 continues to be recovered. This continuation takes place as long as the driver does not press the accelerator pedal PA again or as long as the vehicle speed V has not become zero.

[0056] Thanks to the progressive reduction of the value of the regenerative braking torque in sub-step 20 to greatly limit, or even prevent, the formation of metallic deposits in the cells CE, the intensity of the deceleration decreases progressively and therefore the driver does not realize it initially or at least is not surprised, and, once he has realized it, he can, if he wishes, compensate for the loss of intensity of the deceleration by pressing the brake pedal PF. It will be noted that advantageously the lower the first value vl is due to the outside temperature and / or the current state of charge ece, the less the driver will be aware of the progressive decrease in the deceleration.This significant reduction, or even disappearance, of the surprise effect makes the implementation of the strategy to combat the formation of metallic deposits in the CE cells less dangerous, and prevents the driver from being dissatisfied, or even worried, about the operation of the regenerative braking of his vehicle V. .

[0057] [Fig. 4] schematically illustrates an example of a time evolution diagram (t (in seconds)) of the recharging power prb (in kW) of the cellular battery BC during recharging by braking torque recovery carried out by implementing the control method according to the invention. The instant tl corresponds to the moment when the driver stops pressing the accelerator pedal PA, and therefore the braking torque recovery phase begins with the recovery of a braking torque having the first value vl during the first duration dl (which ends at the instant t2 (i.e. dl = t2 - tl)), which results in a supply of the cellular battery BC with a first recharging power prbl.Then, during the second duration d2 expiring at time t3 (i.e. d2 = t3 -12) the braking torque recovery continues but by varying its value from vl to V2, which results in a power supply to the cellular battery BC which varies from the first recharge power prbl to a second recharge power prb2 (with prb2 < prbl). Then, from time t3, the recovery of a braking torque having the second value v2 continues. Here, at time t4 the driver presses the accelerator pedal PA, and therefore the braking torque recovery phase ends.

[0058] For example, in sub-step 20 of step 10-30 the progressive reduction can be done according to a gradient which is between 3% of the first value vl per second and 15% of the first value vl per second. Preferably, in sub-step 20 of step 10-30 the progressive reduction can be done according to a gradient which is between between 5% of the first value vl per second and 10% of the first value vl per second. But other gradient values ​​can be used. It should be noted, however, that the lower the gradient, the less the gradual decrease in deceleration is felt by the driver, but the longer the second duration d2 will be. For example, the gradient value can be chosen during the development or testing phase of the vehicle V.

[0059] Also for example, in step 10-30 the first v1 and second v2 values ​​can be chosen as a function of the current state of charge ece of the cellular battery BC. It will be understood in fact that the recharging by recovery of braking torque (in the presence of the aforementioned strategy) must not cause the state of charge ece of the cellular battery BC to go above a maximum state of charge (which generally decreases with the aging of the cellular battery BC).

[0060] Also for example, in step 10-30 the first vl and second v2 values ​​can be chosen as a function furthermore of the temperature outside the cellular battery BC and / or of a regenerative braking mode chosen by the driver from at least two modes.

[0061] Also for example, in step 10-30 the first d1 and second d2 durations can be chosen so that their sum (d1 + d2) is less than or equal to a third duration d3 beyond which the cellular battery BC begins to be subject to a metallic deposit on at least one anode of a cell CE, in the presence of a recharging power prb (supplying the cellular battery BC) resulting from a regenerative braking torque which is greater than the second value v2.It will be understood that if the cellular battery BC begins to be subject to a metallic deposit from the end of the third duration d3 (from the start of the braking torque recovery) when the recharge power prb corresponds to a regenerative braking torque v4 greater than v2, then by using a total duration dl + d2 less than the third duration d3 (i.e. dl + d2 < d3) we almost completely prevent the formation of metallic deposit in the cellular battery BC since we will find ourselves before the end of the third duration d3 with a recharge power prb corresponding to a regenerative braking torque less than v4.

[0062] It will also be noted, as illustrated non-limitingly in [Fig.l], that the supervision computer CS (or the computer of the control device DC) can also comprise a mass memory MM1, in particular for storing the current state of charge ece, the possible outside temperature and the possible regenerative braking mode chosen by the driver, as well as possible intermediate data involved in all its calculations and processing. Furthermore, this supervision computer CS (or the computer of the control device DC) can also comprise an input interface IE for receiving at least the current state of charge ece, the possible outside temperature and the possible regenerative braking mode chosen by the driver, to use them in calculations or processing, possibly after having formatted and / or demodulated and / or amplified them, in a manner known per se, by means of a digital signal processor PR2. In addition, this supervision computer CS (or the computer of the control device DC) can also include an output interface IS, in particular to deliver each message (or order) containing a regenerative braking torque instruction.

[0063] It will also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means of the electronic circuit (or hardware) type, such as for example the processor PR1, is capable of implementing the control method described above to control recharging of the cellular battery BC of the land vehicle V by recovery of braking torque by the electric motor MME.

Claims

Claims

1. Method for controlling recharges of a cellular battery (BC) equipping a land vehicle (V) comprising an electric prime mover (MME), coupled to said cellular battery (BC) and capable of recovering braking torque when a driver completely stops pressing an accelerator pedal (PA), characterized in that it comprises a step (10-30) in which, in the event of ceasing to press said accelerator pedal (PA), a braking torque of a first chosen value is recovered with said prime mover (MME) for a first chosen duration, then said recovered braking torque is gradually reduced for a second chosen duration to a second chosen value, then said recovery of braking torque is continued at this second value.

2. Method according to claim 1, characterized in that in said step (10-30) said progressive reduction is made according to a gradient between 3% of said first value per second and 15% of said first value per second.

3. Method according to claim 2, characterized in that in said step (10-30) said progressive reduction is made according to a gradient between 5% of said first value per second and 10% of said first value per second.

4. Method according to one of claims 1 to 3, characterized in that in said step (10-30) said first and second values ​​are chosen as a function of a current state of charge of said cellular battery (BC).

5. Method according to claim 4, characterized in that in said step (10-30) said first and second values ​​are chosen as a function further of a temperature outside said cellular battery (BC) and / or of a regenerative braking mode chosen from at least two modes.

6. Method according to one of claims 1 to 5, characterized in that in said step (10-30) said first and second durations are chosen so that their sum is less than or equal to a third duration beyond which said cellular battery (BC) begins to be the subject of a metallic deposit on at least one anode of a cell (CE) which it (BC) comprises, in the presence of a recharging power, supplying said cellular battery (BC), resulting from a braking torque greater than said second value.

7. Computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing the control method according to one of claims 1 to 6, in a land vehicle (V) comprising a cellular battery (BC) and an electric prime mover (MME), coupled to said cellular battery (BC) and capable of recovering braking torque when a driver completely stops pressing an accelerator pedal (PA), to control recharges of said cellular battery (BC) by recovery of braking torque by said prime mover (MME).

8. Control device (DC) for controlling recharges of a cellular battery (BC) equipping a land vehicle (V) comprising an electric prime mover (MME), coupled to said cellular battery (BC) and capable of recovering braking torque when a driver completely stops pressing an accelerator pedal (PA), characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to carry out the operations consisting, in the event of cessation of pressing on said accelerator pedal (PA), in triggering a recovery by said prime mover (MME) of a braking torque of a first chosen value for a first chosen duration, then a progressive reduction for a second chosen duration of said recovered braking torque down to a second chosen value, then in triggering a continuation of said braking torque recovery at this second value.

9. Land vehicle (V) comprising a cellular battery (BC) and an electric prime mover (MME), coupled to said cellular battery (BC) and capable of recovering braking torque when a driver completely stops pressing an accelerator pedal (PA), characterized in that it further comprises a control device (DC) according to claim 8.

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