Method for controlling a powertrain of a plug-in hybrid vehicle

Abstract

The invention relates to a plug-in hybrid motor vehicle (1) comprising an electronic control unit (8) and a powertrain (5) including at least one electric machine (5E) and a battery (2) adapted to supply said at least one electric machine with electric current, the powertrain being controllable in a sport mode. The invention relates in particular to a method for controlling such a powertrain, comprising: - a step of acquiring the driving mode selected by the driver, and, when sport mode is selected, - a step of acquiring the value of a charge level of the battery, then, as long as sport mode remains selected, - a step of controlling the powertrain so as to regulate the charge level of the battery around a target charge level which is a function of the charge level value acquired at the time sport mode was selected.Figure for the abridged version: Fig.1.

Description

Title of the invention: Method for controlling a powertrain of a plug-in hybrid vehicle Technical field of the invention

[0001] The present invention relates generally to the field of automobiles.

[0002] It applies to a plug-in hybrid vehicle comprising a powertrain which includes a battery of accumulators, at least one electric machine adapted to be supplied with electric current by the battery of accumulators, and an electronic powertrain control unit.

[0003] It relates more particularly to a method of controlling the powertrain by this electronic control unit. State of the art

[0004] The powertrain of a plug-in hybrid vehicle generally includes an electric drivetrain and an auxiliary drivetrain (typically a fuel-powered internal combustion engine coupled to the vehicle's drive wheels).

[0005] The electric traction chain comprises one or more electric machines, with axial and / or radial flux, supplied with current by a battery of accumulators and coupled to the drive wheels of the vehicle.

[0006] The battery is designed to be recharged in two ways. It can be recharged by connecting it to an electrical network (to a fast charging station, to a home's electrical network, etc.). It can also be recharged by an alternator driven by the internal combustion engine.

[0007] When the vehicle is in motion, the ideal is to minimize the internal combustion engine's fuel consumption to reduce the vehicle's pollutant emissions and associated carbon dioxide emissions. This is why owners of plug-in hybrid vehicles are advised to recharge their batteries as often as possible by connecting them to an electrical grid, so that they can begin each new journey with a fully charged battery.

[0008] It is also common to offer a driver a choice of driving modes from among several different modes. The driver can thus choose a dynamic mode, called sport mode, designed to ensure that the vehicle's performance in terms of acceleration and therefore traction to the wheels is optimal.

[0009] Thus, when this mode is selected and the driver seeks to accelerate to the maximum capacity of the vehicle, the internal combustion engine and the electric machine(s) are controlled to deliver their full power.

[0010] In this case, the maximum power that an electrical machine can develop depends not only on its architecture, but often also on the state of charge of the battery.

[0011] Thus, if the battery of accumulators is charged, each electric machine will be able to develop a high power.

[0012] Otherwise, the power output will be limited by the maximum discharge power that the battery can deliver, which depends on its energy level. It will also be limited in time since, once the battery is discharged, only the internal combustion engine will be able to continue propelling the vehicle.

[0013] In this context, one idea would be to use the internal combustion engine to recharge the battery via the alternator as soon as sport mode is selected, so that when the driver wants to accelerate, the battery can deliver a significant amount of energy. However, this method is not entirely satisfactory since it results in high fuel consumption each time the driver selects sport mode when the battery charge level is low.

[0014] More generally, the solution currently used consists, when sport mode is selected, of setting a target charge level which is strictly higher than the minimum charge level of the battery and of controlling the powertrain so that the charge level oscillates as much as possible around this target charge level.

[0015] As explained above, the target charge level could be chosen to be high, but this would not be satisfactory in terms of fuel consumption. Furthermore, there is a risk that, by using sport mode, the driver might become aware that selecting this mode increases the battery's charge level. They might then be tempted to charge the battery (for example, when passing through zero-emission zones) not at a charging station, but by using sport mode in a roundabout way, which would again generate unwanted pollutant and carbon dioxide emissions.

[0016] This is why the solution currently employed consists of choosing a low target charge level. In this way, if the battery charge level is minimal when sport mode is selected, the amount of fuel required to charge the battery will be minimal. Conversely (if the battery charge level is high when sport mode is selected), the vehicle can operate primarily using the energy stored in the battery to propel the vehicle, until the battery charge level reaches the target charge level, which will again allow restricting pollutant and carbon dioxide emissions. It is understood, of course, that this solution is not entirely satisfactory since with a low target charge level, the energy available in the battery will also be low, meaning that the powertrain's performance will not be optimal.

[0017] This is also the reason why a compromise is currently made in the choice by each manufacturer of the target load level. Presentation of the invention

[0018] The present invention proposes a solution that makes it possible to do without any compromise.

[0019] More specifically, the invention proposes a control method as defined in the introduction, comprising: - a step of acquiring the driving mode selected by the driver, and, when sport mode is selected, - a step to acquire the value of a battery charge level, then, as long as sport mode remains selected, - a powertrain control step to regulate the battery charge level around a target charge level which is chosen according to the charge level value acquired when sport mode was selected (hereinafter referred to as "activation value").

[0020] Thus, thanks to the invention, the target charge level can be chosen to be higher the higher the activation value is itself.

[0021] In this way, if the activation value is low, the target load level will itself be low, which will minimize the fuel consumption to achieve it.

[0022] On the other hand, if the activation value is high, the target load level can itself be high, which will guarantee good performance in terms of acceleration without generating excessive fuel consumption.

[0023] Another advantage of this solution is that activating sport mode will never result in a significant recharge of the battery, so the driver will not be able to use this method to recharge the battery. On the contrary, if they wish to benefit from the best possible dynamic performance, they will be encouraged to recharge the battery from electrical grids as much as possible, which will be better for the environment.

[0024] Other advantageous and non-limiting features of the piloting method according to the invention, taken individually or in all technically possible combinations, are as follows: - The target charge level is selected by the electronic control unit from at least two values, including a predetermined lower and upper limit. - The upper limit is selected only if the charge level value acquired at the time sport mode was selected is greater than or equal to the upper limit. - The lower limit is selected only if the charge level value acquired when sport mode was selected is less than or equal to the lower limit. - If the charge level value acquired when sport mode was selected is between the lower and upper limits, the selected target charge level is equal to that value. - when said other driving mode is selected, a step is provided to control the powertrain so as to regulate the charge level of the accumulator battery around another target charge level which is strictly lower than the lower terminal.

[0025] The invention also relates to a plug-in hybrid motor vehicle comprising a powertrain which includes at least one electric machine adapted to be supplied with electric current by a battery of accumulators, and an electronic powertrain control unit, which is programmed to implement a control method as described above.

[0026] Of course, the various features, variants, and embodiments of the invention can be combined with one another in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0027] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0028] On the attached drawings:

[0029] [Fig-1] is a schematic view of a motor vehicle according to the invention;

[0030] [Fig.2] is a graph illustrating the charge level values ​​of a battery of accumulators of the motor vehicle of the [Fig.1] usable within the framework of the control method according to the invention, and also illustrating three examples of evolution of charge level of the accumulator battery.

[0031] In [Fig.1], a motor vehicle 1 land vehicle is shown.

[0032] This motor vehicle 1 could be of any type (motorcycle, truck, bus, etc.). Here, it is a car which conventionally includes wheels and a chassis which supports, in particular, a powertrain 5 and bodywork elements.

[0033] This motor vehicle 1 is of the plug-in hybrid type. Therefore, the powertrain 5 comprises an electric drive chain and a second chain.

[0034] The electric traction chain comprises at least one battery of accumulators (hereinafter referred to as traction battery 2), and at least one electric machine 5E which is supplied with electric current by the traction battery 2 and which is coupled to drive wheels of the motor vehicle 1.

[0035] The second chain preferably comprises a 5T internal combustion engine which is coupled, via a gearbox and a clutch, to the drive wheels of the motor vehicle 1. This 5T internal combustion engine is also coupled to an alternator for recharging the traction battery 2.

[0036] This motor vehicle 1 being of the plug-in hybrid type, it includes at least one charger connected, on one side, to the traction battery 2 and, on the other, to a charging terminal 6 for this battery. This charging terminal 6 is, for example, in the form of a power outlet adapted to be connected to a stationary electrical network such as a charging station capable of delivering high electrical power or a local electrical network of a building capable of delivering lower electrical power.

[0037] The traction battery 2 can be of any type. Here it is of the Lithium-Ion type. It comprises a casing 3 which houses electrochemical cells 4.

[0038] This traction battery 2 has a state of charge (SOC) which is related to the ratio between the battery's instantaneous capacity and its nominal capacity. This state of charge is expressed as a percentage. It is between a minimum threshold SOCmin and a maximum threshold SOCmax (see [Fig. 2]). Here, these two thresholds will be considered to be 0% and 100%, respectively. Of course, alternatively, these thresholds could have different values ​​(particularly if the method for calculating the state of charge is different, or if it is desired to preserve the battery by restricting its operating range).

[0039] This traction battery 2 includes an electronic control unit BMS (from the English "Battery Management System"), hereinafter referred to as BMS unit 7.

[0040] This BMS unit 7 is housed in the casing 3 and it allows measurements of the characteristics of the electrochemical cells 4 to be made. It is particularly suitable for measuring the voltage across the terminals of each of these cells and for deducing the SOC charge level of the traction battery 2.

[0041] The motor vehicle 1 also includes an electronic powertrain control unit 5.

[0042] This electronic control unit is here formed by a computer 8 which includes a processor, a storage unit (hereafter referred to as memory), and a communication interface.

[0043] Thanks to this interface, the calculator 8 is adapted to communicate with the BMS unit 7.

[0044] Its memory records data used in the process described below.

[0045] It records, in particular, two predetermined charge level values ​​called the lower terminal SOCinf and the upper terminal SOCsup. These values ​​are described as predetermined in that they are defined by the manufacturer. They may vary depending, in particular, on the battery's state of health (SOH) and / or the ambient temperature.

[0046] These two limits are preferably distinct from the minimum threshold SOCmin and the maximum threshold SOCmax (see [Fig.2]). They are, for example, equal to 20% and 90%.

[0047] The memory also stores a computer application, consisting of computer programs including instructions whose execution by the processor allows the implementation by the computer 8 of the process described below.

[0048] The vehicle also includes a Human-Machine Interface (HMI) which is adapted to communicate with the computer 8 and which allows the driver to select a driving mode from among several modes.

[0049] This Human-Machine Interface (HMI) can be formed by a dedicated button or by a touch screen offering various functions including that of selecting the driving mode.

[0050] Thus, the driver can choose a driving mode from among at least two different modes. In particular, they can select a normal mode and a more dynamic mode than the normal mode, called sport mode. In this sport mode, the vehicle must be able to accelerate faster than in any other mode.

[0051] We can then describe how the computer proceeds when the sport mode is selected so that the vehicle can offer good performance in terms of acceleration, without excessively relying on the internal combustion engine to recharge the traction battery 2, in order to reduce the fuel consumption of this engine.

[0052] In a first step, the computer 8 acquires the driving mode selected by the driver.

[0053] While normal mode is selected, the control unit 8 manages the powertrain 5 to regulate the SOC charge level of the traction battery 2 around a low target SOC0, less than or equal to 10% (typically equal to 8%). This low target is chosen to ensure that when the vehicle reaches its destination, it will have significantly discharged its traction battery 2 and thus minimized its fuel consumption.

[0054] At this stage, we can define a "regulation" as an algorithm which aims to ensure that the SOC charge level of the traction battery 2 tends towards a target, except when constraints prevent it from doing so.

[0055] These constraints are of two types here.

[0056] They are primarily related to the environment. For example, when the motor vehicle 1 is traveling downhill, the SOC charge level of the traction battery 2 may exceed the target. Conversely, when going uphill, it may fall below this target.

[0057] The constraints are also linked to the driver's actions. Thus, when the driver drives in a sporty manner, the SOC charge level of the traction battery 2 may fall below the target, the objective remaining in fact to offer the driver good dynamic performance, even if it means completely discharging the traction battery 2.

[0058] In the absence of such constraints, typically when the motor vehicle 1 is traveling at a constant speed and less than 130 km / h on a horizontal road, the regulation will bring the SOC charge level of the traction battery 2 back towards the target.

[0059] In other words, this regulation can be based on a classic regulation loop (typically using a PI or PID controller) at the output of which a calculation stage will be added allowing a tolerance to take into account the aforementioned constraints.

[0060] We can now describe how the control unit 8 proceeds when sport mode is selected. During a second step (as soon as sport mode has been selected), the control unit acquires the SOC charge level value of the battery accumulator 2. This value is stored in its memory and will hereafter be referred to as the SOCa activation value.

[0061] Next, the computer controls the powertrain 5 so as to regulate the SOC charge level of the traction battery 2 around a target SOCc charge level.

[0062] This target charge level SOCc has a value that is always greater than the low target SOC0 (typically greater than 10%) and that is defined according to the SOCa activation value.

[0063] The value of this target SOCc load level is defined once, at the time of activation of sport mode, and then preferentially remains invariable until sport mode is deactivated (or until the powertrain 5 is stopped if sport mode is not deactivated in the meantime).

[0064] The target charge level SOCc is determined such that its value is maximized while minimizing the fuel consumption required to reach it. The control system is then used to bring the charge level SOC of the traction battery 2 towards this target charge level SOCc.

[0065] In practice, this target SOC load level is chosen from three values: - the lower bound SOCinf, - the SOCa activation value, and - the upper bound SOCsup.

[0066] The lower bound SOCinf is chosen only if the SOCa activation value is less than or equal to the lower bound SOCinf.

[0067] As shown by curve C3 in [Fig. 2], in this configuration, when sport mode is selected at time tb, the battery charge is low. Therefore, the internal combustion engine is used to recharge the traction battery 2 so that its charge level SOC tends towards the lower terminal SOCinf. Its value then oscillates around this terminal due to the stresses exerted on the battery by the driver and the environment.

[0068] It is noted here that this lower limit SOCinf is strictly greater than the threshold SOCo, which guarantees even in this eventuality that the vehicle offers better dynamic performance in sport mode than in normal mode.

[0069] The upper limit SOCsup is chosen as the target charge level SOCc only if the activation value SOCa is greater than or equal to the upper limit SOCsup.

[0070] As shown by curve Cl in [Fig. 2], in this configuration, when sport mode is selected at time tb, the traction battery 2 is fully charged. It can therefore be used by the electric motor to propel the vehicle until its charge level SOC is substantially equal to the upper limit SOCsup. Its value then fluctuates around this limit due to the stresses exerted on the battery by the driver and the environment.

[0071] It should be noted here that the upper limit SOCsup is lower than the maximum threshold SOCmax, which allows the charge level SOC to oscillate freely above this limit, for example when the vehicle is going downhill or when it brakes.

[0072] Otherwise, the SOCa activation value is chosen as the target charge level SOCc. Thus, the new target is equal to the charge level at the time the driver selects sport mode, so that no battery recharging by the combustion engine is necessary to reach it and that the dynamic performance is the best possible without recharging.

[0073] As shown by curve C2 on [Fig.2], in this configuration, as soon as sport mode is selected at time tb the SOC charge level of the traction battery 2 then oscillates around its SOCa activation value, due to the constraints exerted on the battery by the driver and the environment.

[0074] The present invention is in no way limited to the embodiment described and represented, but a person skilled in the art will be able to make any variation in accordance with the invention.

[0075] The target charge level could be selected from two predetermined values ​​(for example, the lower and upper limits). Thus, the selected target charge level could be chosen to be equal to the limit that is closest to the activation value. Alternatively, the selected target charge level could be the upper limit if the activation value is greater than that limit, and the lower limit otherwise.

[0076] Alternatively, the target load level could be chosen from more predetermined values, in which case the selected target will preferably be the predetermined value just below the activation value.

[0077] As an alternative, the invention could be applied to an electric vehicle equipped with a range extender (typically a fuel cell or a small internal combustion engine decoupled from the drive wheels).

Claims

Demands

1. A method for controlling, by means of an electronic control unit (8), a powertrain (5) of a plug-in hybrid motor vehicle (1), the powertrain (5) comprising at least one electric machine (5E) and a battery (2) adapted to supply said at least one electric machine (5E) with electric current, the powertrain (5) being controllable according to at least two distinct driving modes selectable by a driver of the motor vehicle (1), including a sport mode that is more dynamic than another driving mode, the control method comprising: - a step of acquiring the driving mode selected by the driver, and, when the sport mode is selected, - a step of acquiring the value (SOCa) of a state of charge (SOC) of the battery (2), then, as long as the sport mode remains selected,- a powertrain control step (5) to regulate the state of charge (SOC) of the accumulator battery (2) around a target state of charge (SOCc), characterized in that the target state of charge (SOCc) is a function of the state of charge (SOC) value (SOCa) acquired at the time when sport mode was selected.

2. A control method according to claim 1, wherein the target charge level (SOCc) is chosen by said electronic control unit (8) from among at least two values, including a predetermined lower bound (SOCinf) and upper bound (SOCsup), the upper bound (SOCsup) being chosen only if the charge level (SOC) value (SOCa) acquired at the time when sport mode was selected is greater than or equal to the upper bound (SOCsup).

3. A control method according to claim 2, wherein the lower limit (SOCinf) is chosen only if the value (SOCa) of charge level (SOC) acquired at the time when sport mode was selected is less than or equal to the lower limit (SOCinf).

4. A control method according to claim 2 or 3, wherein, if the charge level (SOC) value (SOCa) acquired at the time sport mode was selected is between the lower bound

5.

6. (SOCinf) and the upper bound (SOCsup), the chosen target charge level (SOCc) is equal to said value (SOCa). A control method according to any one of claims 2 to 4, wherein, when said other driving mode is selected, a step is provided for controlling the powertrain (5) so as to regulate the charge level (SOC) of the accumulator battery (2) around another target charge level (SOC0) which is strictly lower than the lower limit (SOCinf). plug-in hybrid motor vehicle (1) comprising a powertrain (5) which includes at least one electric machine (5E) adapted to be supplied with electric current by a battery of accumulators (2), and an electronic control unit (8) of the powertrain (5), characterized in that the electronic control unit is programmed to implement a control method according to one of claims 1 to 5.

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