METHOD FOR MANAGING A CHARGE STATE OF AN ELECTRICAL ENERGY STORAGE ELEMENT OF A DRIVE UNIT, AS WELL AS DRIVE UNIT AND VEHICLE

Description

[0001] The present invention relates to the field of hybrid powertrains and more particularly concerns a method of managing the charge level of an electrical energy storage element within such a powertrain.

[0002] Hybrid technology consists of a combination of a combustion engine and an electric motor, each contributing to the operation of the vehicle, thus resulting in lower fuel consumption, particularly for the purpose of environmental preservation.

[0003] Among the various hybrid technologies available in the automotive industry, some involve vehicle propulsion entirely powered by the electric motor. The internal combustion engine's primary function is to recharge an electrical energy storage unit, which in turn supplies power to the electric motor. These technologies are commonly referred to as "series hybrid" technologies. A specific application of these "series hybrid" technologies is the range extender. When the vehicle's electric range is depleted (i.e., the battery is empty), the internal combustion engine starts to recharge the battery, thus extending the vehicle's range, for example, to an electric charging station.

[0004] One drawback of this type of powertrain is that the internal combustion engine operates at a single operating point. When the internal combustion engine has only one operating point, the energy it produces and which is transferred to the electrical energy storage unit remains constant over time. Consequently, depending on the vehicle's electrical consumption, the energy supplied by the internal combustion engine to the electrical energy storage unit may be insufficient or, conversely, excessive.

[0005] Insufficient energy supply leads to the discharge of the electrical energy storage system in the medium to long term, and therefore tends to reduce the vehicle's range. Conversely, if the internal combustion engine operates at a single operating point, resulting in consistently high engine activity, then the engine tends to wear out more quickly.

[0006] For example, document WO2020170634 describes a process that presents this type of drawback.

[0007] DE 10 2010 024896 A1 presents a modular hybrid drive, particularly for the propulsion of passenger cars. The drive features an electrodynamic drive unit that can optionally function as an electric generator. A thermodynamic drive unit comprises a four-stroke combustion engine, where the interactive control of the thermodynamic drive unit's throttle is achieved via rotary servo valves. The two drive units and a coupling unit are formed as separate modules combined in a series arrangement and mechanically connected to the two axial ends of a working shaft using a standardized connection technique such that the power from each module in the series arrangement is transferred to the working shaft.

[0008] EP 3418532 A1 presents a device for adjusting the compression ratio of an internal combustion engine. This adjustment device comprises: a connecting rod including a small end, a big end for receiving a crankshaft of the engine, and a connecting rod body connecting the small end to the big end; a piston including a piston shaft; an eccentric comprising a main shaft installed at the small end of the connecting rod and having an eccentric bore receiving the piston shaft; a lever cooperating with the main shaft so as to rotate the main shaft by pivoting the lever; at least one actuating element being connected on one side to the connecting rod body and on the other side to the lever so as to pivot the lever. According to the invention, the connecting rod and the actuating element are respectively made of materials having different coefficients of thermal expansion.

[0009] The present invention aims to overcome such a drawback by proposing a method for managing the charge level of an electrical energy storage element of a powertrain of a hybrid motor vehicle, said powertrain comprising at least one electric motor driving the vehicle by itself, at least one generator set comprising a thermal engine driving an electric generator, the thermal engine being capable of operating at at least two compression ratios, the electrical energy storage element storing the electrical energy produced by the generator, the management method controlling the thermal engine at a first compression ratio or a second compression ratio depending on the charge level of the electrical energy storage element and / or the electrical consumption of the electric motor,characterized in that the heat engine is maintained at the first compression ratio when the charge level of the electrical energy storage element is above a lower charge state threshold and below a higher charge state threshold, the higher charge state threshold being greater than the lower charge state threshold, and the heat engine is switched to the second compression ratio when the charge level of the electrical energy storage element is below the lower charge state threshold. According to the invention, the second compression ratio is the higher of the two compression ratios.

[0010] Thus, with a heat engine having two compression ratios, the electrical energy supplied by the electric generator can be adapted to match the consumption of the electric motor, while limiting a potential superfluous overactivity of the heat engine that could accelerate its wear in the medium or long term.

[0011] The electric motor is directly connected to the vehicle's drivetrain and manages its propulsion. When we say that the vehicle's propulsion is managed solely by the electric motor, we mean that the vehicle's propulsion is provided exclusively by the electric motor; the internal combustion engine is never involved in setting the vehicle in motion.

[0012] The electric motor is powered by an electrical energy storage unit. This unit is, for example, a battery capable of storing a quantity of electrical energy to supply to the electric motor when needed. The charge level of the electrical energy storage unit decreases when the electric motor is running and the storage unit is not being recharged simultaneously. The rate at which the electric motor consumes electrical energy can vary depending on several vehicle-related parameters, such as its weight and the vehicle's speed.

[0013] The generator's function is to supply electrical power to the aforementioned electrical energy storage unit, that is, to maintain or increase its charge level. The internal combustion engine comprises a moving assembly equipped with at least one piston that compresses a combustion mixture to generate an explosion and thus mechanical energy. This mechanical energy is transmitted to the electric generator, which converts the mechanical energy generated by the internal combustion engine into electrical energy. This electrical energy is then transmitted to the electrical energy storage unit to charge it.

[0014] The internal combustion engine is a two-compression engine, meaning that the pistons within it can compress at two different ratios. The air-fuel mixture is compressed in the piston's combustion chambers to varying degrees. The higher the compression ratio, the greater the mechanical energy released by the explosion. Therefore, if the internal combustion engine can operate at two different compression ratios, it means it can generate mechanical energy at two different levels. The electric generator, which is directly connected to the internal combustion engine, thus provides two different levels of power.

[0015] It is understood that according to one aspect of the invention the heat engine is put into operation only according to the first compression ratio or according to the second compression ratio.

[0016] The first compression ratio is lower than the second compression ratio. Therefore, the mechanical energy generated by the heat engine is less if the heat engine operates at the first compression ratio than if it operates at the second compression ratio.

[0017] Thanks to the two compression ratios of the thermal engine, the electric generator can thus provide an electrical energy input adapted to a consumption of the electrical energy stored by the electrical energy storage element and consumed by the electric motor.

[0018] The charge level management system for the electrical energy storage element determines the optimal compression ratio for a given charge level and can also switch between different compression ratios based on the energy storage element's charge level. This management system extends the vehicle's electric range without overworking the internal combustion engine.

[0019] The switching between compression ratios can also depend on the electric motor's power consumption. Power consumption is primarily dependent on vehicle speed. Therefore, the higher the vehicle's speed, the greater the power consumption.

[0020] Depending on the vehicle's speed, for example whether it is traveling in the city or on a highway, the compression ratio of the internal combustion engine can switch in order to adapt to the electrical consumption of the electric motor resulting from said vehicle speed.

[0021] Since the first compression ratio is the lowest, it is possible that despite the generator's power generation, the charge level of the electrical energy storage element may decrease. This is because the electric motor consumes electrical energy more rapidly than the combined heat engine and generator supply. In this situation, the charge level of the electrical energy storage element decreases.

[0022] The charge level of the electrical energy storage element may fall below the low state of charge threshold. Exceeding this low state of charge threshold indicates that electrical energy consumption is too high relative to the electrical energy input from the generator set. The management system therefore switches the internal combustion engine to its second compression ratio, which is the higher of the two compression ratios, thereby increasing the mechanical energy generated by the internal combustion engine. Switching to the second compression ratio ensures an increase in the charge level of the electrical energy storage element, or, in the worst-case scenario, slows the decline in the charge level of the electrical energy storage element if the electric motor is consuming too much energy.

[0023] The internal combustion engine is maintained at the first compression ratio as long as the charge level of the electrical energy storage element is below the upper charge threshold. The upper charge threshold corresponds to a high charge level approaching the maximum charge level of the electrical energy storage element.

[0024] According to a feature of the process, the heat engine is maintained at the second compression ratio after the charge level of the electrical energy storage element falls below the lower charge state threshold and as long as the charge level of the electrical energy storage element is below the upper charge state threshold, and the operation of the heat engine is interrupted when the charge level of the electrical energy storage element is above the upper charge state threshold.

[0025] The principle is the same as for crossing the low state of charge threshold mentioned previously, but here for a high charge level. Once the charge level of the electrical energy storage element has crossed the low state of charge threshold and is below it, the internal combustion engine switches to the second compression ratio as described earlier. The energy generated by the generator then increases the charge level of the electrical energy storage element. When the latter crosses the high state of charge threshold and becomes above it, the internal combustion engine shuts off to conserve vehicle fuel, as the charge level of the electrical energy storage element is sufficiently high that it does not need to be supplied by the electrical energy generated by the generator.Turning off the internal combustion engine also helps to reduce pollutant emissions.

[0026] According to one feature of the process, the internal combustion engine is kept off as long as the charge level of the electrical energy storage element is above the upper state of charge threshold, and it is started when the charge level of the electrical energy storage element falls below the upper state of charge threshold. A charge level above the upper state of charge threshold is sufficient for the generator set to avoid generating power. The internal combustion engine can therefore be switched off for a period of time during which the charge level of the electrical energy storage element remains above the upper state of charge threshold.

[0027] As soon as the charge level crosses the upper charge threshold and falls below it, the internal combustion engine is started. During startup, the internal combustion engine may, for example, operate by default at the first compression ratio, or at the compression ratio most compatible with the electrical consumption of the electric motor at the time the internal combustion engine starts, for example, at the second compression ratio if the electric motor consumes a significant amount of electrical energy.

[0028] According to a characteristic of the process, the lower threshold of state of charge is between 5% and 60% of a maximum charge level of the electrical energy storage element.

[0029] According to a characteristic of the process, the upper threshold of state of charge is between 40% and 100% of a maximum charge level of the electrical energy storage element.

[0030] According to a characteristic of the process, the internal combustion engine is controlled at either the first or second compression ratio, depending on the electric motor's power consumption, as long as the charge level of the electrical energy storage element is below the upper charge threshold and above the lower charge threshold. As previously stated, the internal combustion engine is stopped while the charge level of the electrical energy storage element is above the upper charge threshold and defaults to the second compression ratio when the charge level falls below the lower charge threshold.

[0031] In other scenarios, the internal combustion engine's compression ratio can switch between the two ratios depending on the electric motor's power consumption, which is related to the vehicle's speed. The higher the vehicle's speed, the more the management system tends to switch the internal combustion engine to the second compression ratio.

[0032] According to a characteristic of the process, the change in the internal combustion engine's compression ratio is controlled by a control module. This control module is capable of receiving information and issuing commands based on that information. The control module is therefore able to command the internal combustion engine to switch from the first compression ratio to the second compression ratio, and vice versa.

[0033] The control module receives an indication of the charge level of the electrical energy storage unit. Based on this indication, the control module decides whether or not to send a command to the internal combustion engine to change its compression ratio. After receiving the charge level of the electrical energy storage unit, the control module compares it with the high or low charge threshold and commands the internal combustion engine to change its compression ratio.

[0034] According to one feature of the method, the control module receives an indication of the electric motor's power consumption. Just as with receiving an indication of the charge level of the electrical energy storage element, the control module can receive a change in the electric motor's power consumption. This indication can be provided by the electric motor or by the electrical energy storage element. Receiving the indication of the electric motor's power consumption can allow the compression ratio to be adjusted to match said power consumption. The invention also covers a powertrain for a motor vehicle implementing a method for managing the charge level of an electrical energy storage element as described above.In order to carry out the implementation of the charge level management process of the electrical energy storage element, the powertrain includes all the elements mentioned so far, namely the electric motor, the electrical energy storage element and the generator set equipped with the thermal engine and the electric generator.

[0035] According to one feature of the invention, the heat engine comprises a moving assembly equipped with at least one crankshaft, at least one piston, and at least one connecting rod linking the piston to the crankshaft. This connecting rod includes a means for adjusting the piston height to operate the heat engine at the first or second compression ratio. The crankshaft, via the connecting rod, drives the piston in a cylinder. The piston thus compresses the gas present in the cylinder. It is as a result of this compression that mechanical energy is generated by the heat engine, which is subsequently supplied to the electrical energy storage element after conversion into electrical energy by the electric generator.

[0036] The connecting rod has one end connected to the crankshaft and the other to the piston. The crankshaft generates a rotary motion which, via the connecting rod, becomes a linear motion of the piston within the cylinder.

[0037] The piston height adjustment mechanism acts on the connecting rod, causing the connecting rod to move the piston and thus compress the gas in the combustion chamber to a greater or lesser degree. It is thanks to this adjustment mechanism that the internal combustion engine can vary between the first and second compression ratios. Therefore, when the previously mentioned control system sends a command to the internal combustion engine resulting in a change in the compression ratio, it is specifically the adjustment mechanism that is activated and modifies the piston height to achieve a greater or lesser degree of compression.

[0038] According to one feature of the invention, the piston height adjustment means comprises at least one eccentric bearing carrying a piston pin, the position of which is controlled by two control members mounted on the connecting rod. The eccentric bearing is located at the connection between the connecting rod and the piston. The two control members are capable of modifying the position of the eccentric bearing, for example, by means of an oil circuit or a spring system. When the eccentric bearing changes position, the piston height is modified, thereby changing the compression exerted by the piston and thus altering the compression ratio of the internal combustion engine.

[0039] The invention also covers a motor vehicle comprising a powertrain as described above, the electric motor propelling the motor vehicle being electrically powered by the electrical energy storage element, while the generator electrically charges the electrical energy storage element. As described above, the propulsion of such a motor vehicle is entirely electric. Depending on the type of vehicle, the two compression ratios of the powertrain may vary. Thus, for example, the compression ratios of the internal combustion engine in a commercial vehicle differ from those of the internal combustion engine in a city car, as the electrical energy requirements of the electric motor are not the same.

[0040] In another example, the two compression ratios are identical, and it is the utilization rate of each ratio that varies depending on the type of vehicle. Thus, a city car will tend to primarily use the first compression ratio, while a commercial vehicle, due to its weight when loaded, for example, will tend to primarily use the second compression ratio. Such an example allows for the standardization of internal combustion engine manufacturing.

[0041] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which: [ fig 1 ] is a general diagram of a powertrain capable of implementing a method for managing the charge level of an electrical energy storage element according to the invention, [ fig 2 ] is a graph detailing a sequence of the management process, [ fig 3 ] is a diagram of a moving assembly of a heat engine that equips the powertrain according to the invention, [ fig 4 ] is a diagram of a connecting rod of this moving assembly.

[0042] THE figure 1 represents a powertrain 1 arranged within a hybrid motor vehicle. This powertrain 1 comprises an electric motor 2 and a generator 4 equipped with an internal combustion engine 5. It is therefore a series hybrid powertrain 1. The distinctive feature of the powertrain 1 according to the invention is that only the electric motor 2 provides propulsion for the vehicle. The internal combustion engine 5 therefore has no function in propelling the vehicle. Consequently, only the electric motor 2 is connected to a drivetrain 7 of the vehicle.

[0043] The powertrain 1 includes an electrical energy storage element 3. The function of the electrical energy storage element 3 is to store electrical energy and supply electrical energy to the electric motor 2 so that the latter can perform its propulsion function. The electrical energy storage element 3 can, for example, be a battery that stores electrical energy in order to release it to the electric motor 2, as required. When the vehicle is stationary, the electrical energy storage element 3 can be recharged, for example, via a domestic or urban electrical grid.

[0044] When the vehicle is running, the electrical energy storage unit 3 is recharged by the generator 4, which is therefore integrated into the vehicle. The internal combustion engine 5 operates by fuel injection. When the internal combustion engine 5 is running, it generates mechanical energy. Details concerning the generation of mechanical energy by the internal combustion engine 5 will be described later.

[0045] The generator set 4 also includes an electric generator 6. The electric generator 6 receives the mechanical energy generated by the internal combustion engine 5 and converts it into electrical energy. Having done this, the electric generator 6 transmits the electrical energy to the electrical energy storage unit 3. Thus, when the vehicle is running, the electric motor 2 consumes the electrical energy stored in the electrical energy storage unit 3 in order to propel the vehicle. However, since the internal combustion engine 5 is also running, the electrical energy storage unit 3 receives an additional supply of electrical energy from the generator set 4, specifically from the electric generator 6. The electrical energy storage unit 3 therefore serves simultaneously to power the electric motor 2 and to store the electrical energy supplied by the electric generator 6.

[0046] The electrical power consumption of the electric motor 2 can vary during a vehicle journey. For example, the electric motor 2 consumes more electrical energy if the vehicle is traveling on a highway, or more generally if the vehicle's speed is high. Consequently, the electrical energy storage element 3 may discharge faster than it recharges.

[0047] It can also happen that the electrical energy storage element 3 recharges faster than it discharges. In this situation, when the electrical energy storage element 3 is fully or almost fully charged, there is no need to run the internal combustion engine 5, as the electrical energy stored in the element 3 is sufficient. Running the internal combustion engine 5 to generate excessive energy is therefore unnecessary and accelerates wear on the engine. It is therefore important to limit wear on the internal combustion engine 5, but without completely depleting the electrical energy storage element 3, which would reduce the vehicle's range.

[0048] To regulate the charge level of the electrical energy storage element 3, the heat engine 5 is a so-called two-compression-ratio heat engine. In other words, the heat engine 5 can operate according to a first compression ratio or a second compression ratio, these two compression ratios being different from each other, and the second compression ratio being the higher of the two compression ratios.

[0049] Changing the compression ratio of the heat engine 5 changes the amount of mechanical energy transmitted to the electric generator 6 and therefore to the electrical energy storage element 3. Thus, the heat engine 5 is able to generate an amount of mechanical energy which corresponds to an amount of electrical energy consumed by the electric motor 2, so that the charge level of the electrical energy storage element 3 oscillates without completely discharging or being completely charged.

[0050] In order to control the charge level of the electrical energy storage element 3, the powertrain 1 includes a control module 8. The control module 8 receives indications relating to the charge level of the electrical energy storage element 3 as well as the electrical consumption of the electric motor 2, also transmitted via the electrical energy storage element 3. These indications can be transmitted in real time, or on a punctual basis at regular time intervals.Depending on the received load level and / or the electrical consumption of the electric motor 2, the control module 8 is capable of transmitting a command to the internal combustion engine 5 so that the latter switches from the first compression ratio to the second compression ratio, or vice versa, depending on the received load level of the electrical energy storage element 3, the electrical consumption of the electric motor 2, and the compression ratio of the internal combustion engine 5 at time t. In order for the powertrain 1 to operate in this way, it is capable of implementing a method for managing the load level of the electrical energy storage element 3 and / or the electrical consumption of the electric motor 2 as described below.

[0051] There figure 2 is a graphic illustration of the management process 10 of the charge level 12 of the electrical energy storage element. The figure 2 is presented in the form of four curves that evolve over time. Thus, if we traverse each of the curves from bottom to top of the figure 2 , the first curve represents an evolution of the electrical consumption 11 by the electric motor over time, the second curve represents an evolution of the charge level 12 of the electrical energy storage element over time, the third curve represents an activity of the first compression ratio 15 of the heat engine over time, and the fourth curve represents an activity of the second compression ratio 16 of the heat engine over time.

[0052] Regarding the activity curves for compression ratios 15 and 16 of the internal combustion engine, position 1 indicates that the engine is operating at the specified compression ratio, while position 0 indicates that the engine is not using that compression ratio. Since the internal combustion engine can only operate at one compression ratio at a time, when one compression ratio is in use, the other is necessarily not.

[0053] Regarding the charge level evolution curve 12 of the electrical energy storage element, the associated graph includes two horizontal lines represented by dashed lines. These lines correspond to a low charge level threshold 13 and a high charge level threshold 14.

[0054] The time sequence for all the curves corresponds to a journey undertaken by a vehicle equipped with the powertrain described above. Thus, at the start of the vehicle, the electrical consumption 11 is zero. Conversely, the charge level 12 is at its maximum, for example, following a complete recharge of the electrical energy storage element before starting.

[0055] At startup, the vehicle travels at a moderate speed, for example in urban driving. Electrical consumption 11 therefore increases, but only slightly. Due to the maximum load level 12, the internal combustion engine is off and therefore not operating at either compression ratio 15, 16. Because the internal combustion engine is inactive, the load level 12 decreases.

[0056] This drop in charge level is such that it is represented on the figure 2 , up to a first instant T1. The first instant T1 corresponds to the moment when the charge level 12 of the electrical energy storage element crosses and becomes lower than the upper charge state threshold 14. Crossing the upper charge state threshold 14 triggers the ignition of the internal combustion engine so that it can generate mechanical energy that can be converted by the electric generator to recharge the electrical energy storage element. Since the electrical consumption 11 is still increasing only slightly, the first compression ratio 15 is used, and therefore switches to position 1 as shown in the diagram. figure 2 .

[0057] Thus, since the energy input from the generator is roughly equivalent to the electrical consumption 11, the charge level 12 continues to decrease, but more slowly than during the period prior to the first instant T1. A slight latency can be observed between the ignition of the internal combustion engine and the change in the slope of the charge level 12 of the electrical energy storage element. This latency corresponds to the time required for the internal combustion engine between its ignition and its regular generation of mechanical energy. In accordance with what was described in figure 1 , the control module receives directly or regularly the charge level 12 of the electrical energy storage element and was thus able, at the first instant T1, to trigger the start-up of the thermal engine.

[0058] The evolution of each parameter of the management process 10 continues in this way, up to a second time point T2. From this second time point T2 onward, the vehicle's electrical consumption 11 increases sharply. This increase may be due to an increase in the vehicle's average speed, for example, if it is operating on a highway cycle. In such a situation, the vehicle's speed increases, and therefore the electrical consumption 11 also increases.

[0059] At the second instant T2, the first compression ratio 15 is still used. Since the electrical consumption 11 is much higher, while the electrical energy generation by the generator remains the same as at the beginning of the journey, the charge level 12 drops, as can be seen on the figure 2 from the second instant T2. To compensate for this, the indication of the increase in electrical consumption 11 of the electric motor transmitted to the control module allows the latter to switch the internal combustion engine according to the second compression ratio 16. The latter therefore moves to position 1 on the figure 2 , while the first compression rate moves to position 0 because it is no longer used.

[0060] Following the example of the figure 2 The second compression ratio 16 is higher than the first compression ratio 15. Therefore, the generator produces more electrical energy when operating at the second compression ratio 16. The electrical energy input is thus higher and compensates for the electric motor's power consumption, even though the vehicle is still traveling at high speed, resulting in significant electric motor consumption. Consequently, the drop in charge level 12 observed from the second instant T2 becomes less pronounced thereafter, almost instantaneously.

[0061] From a third instant T3, the vehicle is again traveling at a moderate speed, for example on a rural road, just as it was during the period preceding the first instant T1. The electrical consumption 11 is therefore lower than when the vehicle was traveling at high speed. The internal combustion engine is still operating at the second compression ratio 16, but the control module, having received the indication of the decrease in electrical consumption 11, switches the engine back to the first compression ratio 15. We thus see the load level 12 rise due to the high energy input from the generator set resulting from the recent use of the second compression ratio 16, then the load level 12 falls slightly again, as the internal combustion engine is once again operating at the first compression ratio 15.

[0062] The charge level 12 continues to fall until a fourth instant T4. This fourth instant T4 corresponds to the moment when the charge level 12 crosses the lower charge state threshold 13 and thus becomes lower than it. The fact that the charge level 12 falls below the lower charge state threshold 13 means that little energy remains in the electrical energy storage element to power the electric motor.

[0063] Thus, at the fourth instant T4, the control module receives the indication of the charge level 12 of the electrical energy storage element and sends a command to the thermal engine in response to the fact that the charge level 12 is below the low threshold of the state of charge 13. The thermal engine thus switches back from the first compression ratio 15 to the second compression ratio 16.

[0064] Therefore, from the fourth instant T4, the charge level 12 rises again thanks to the switching of the thermal engine towards the second compression ratio 16.

[0065] At a fifth instant T5, the charge level 12 crosses the upper charge state threshold 14. The control module then detects that the charge level 12 has crossed the upper charge state threshold 14. The charge level 12 is therefore greater than the upper charge state threshold 14.

[0066] To stop the increase in load level 12 and prevent the internal combustion engine from running unnecessarily at high RPM, the control module commands the internal combustion engine to shut down. This is illustrated in the figure 2 by the passage of the second compression ratio 16 to position 0. At the fifth instant T5, the charge level 12 rises for a time lag, then falls again, the electrical energy storage element no longer receiving energy from the generator set since the thermal engine is off.

[0067] Therefore, a sixth instant T6 is represented on the figure 2 The situation at the sixth instant T6 is identical to the situation at the first instant T1, that is to say that the charge level 12 crosses the high threshold of the state of charge 14. The internal combustion engine is then restarted according to the first compression ratio 15. The situation after the sixth instant T6 is then identical to that after the first instant T1, that is to say with a low electrical consumption 11 and a small drop in the charge level 12.

[0068] The management process 10 is thus capable of oscillating the charge level 12 of the electrical energy storage element between the low charge state threshold 13 and the high charge state threshold 14 so that the electrical energy storage element does not discharge completely or charge completely, so that the electric motor can ensure the propulsion of the vehicle continuously, without the internal combustion engine being unnecessarily pushed to its maximum efficiency.

[0069] There figure 3 This schematically represents the lower end of a two-compression-ratio internal combustion engine 5. Such an internal combustion engine 5 comprises a moving assembly 20. This assembly includes at least one crankshaft 21, at least one piston 22, and at least one connecting rod 23 linking the crankshaft 21 to the piston 22. The rotational motion of the crankshaft 21 is transformed into a translational motion of the piston 22 within a cylinder 24 by means of the connecting rod 23. The piston 22 moves between a top dead center and a bottom dead center, the top dead center varying according to the compression ratio used for the internal combustion engine.

[0070] The two compression ratios of the internal combustion engine 5 result from the fact that the height of the pistons 22 can be changed as they move within their respective cylinders 24. Thus, by changing their height, each piston 22 is able to compress the air-fuel mixture in its respective cylinder 24 to a greater or lesser degree. The higher the pressure within the combustion chamber, the greater the amount of mechanical energy generated. The top dead center of the pistons 22 is modified via each of the connecting rods 23 linking the pistons 22 to the crankshaft 21.

[0071] There figure 4 This represents an example of a connecting rod design 23 that allows for variation in piston height, and consequently, the compression ratio. The connecting rod 23 comprises a small end 33 connected to the crankshaft and a big end 34 which carries the piston.

[0072] The connecting rod 23 contributes to changing the compression ratio by including a means 30 for adjusting the height of the piston to which the connecting rod 23 is connected. The adjustment means includes an eccentric 31 housed in the connecting rod head 34, and two pilot members 32 arranged on either side of a connecting rod body that connects the connecting rod head 34 to the connecting rod foot 33, and which extend to the connecting rod foot 33.

[0073] More particularly, the piloting member 32 includes a rod 36 connected to the eccentric 31 on one side, and to a slide 37 on the other, capable of sliding within a chamber 35 formed in the connecting rod foot 33.

[0074] When, according to the management process described above, the control module switches the internal combustion engine to the second compression ratio, this causes the slide 37 to move along the chamber 35, towards the second port 34. The movement of the slide 37 can, for example, be achieved by the influx of oil (not shown), which exerts pressure on the slide 37 and causes it to move. Each of the slides 37 of the two control elements 32 can be moved in this way.

[0075] The movement of the slides 37 drives each of the rods 36, thus changing the position of the eccentric 31. Changing the position of the eccentric 31 changes the position of the piston's top dead center, causing it to rise to a higher height. Consequently, the compression ratio of the internal combustion engine is altered. To switch between compression ratios, oil is sent into one or the other of the chambers 35, causing the internal combustion engine to switch to either the first or second compression ratio. The position of the eccentric 31 is then also changed, lowering the piston height and resulting in lower pressure within the combustion chamber. The oil inlet and outlet are controlled by the control module based on information received regarding the charge level of the electronic storage element or the electrical consumption of the electric motor.

[0076] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention as defined by the claims.

[0077] The invention, as just described, achieves its intended purpose and provides a method for managing the charge level of an electrical energy storage element implemented by a powertrain comprising a thermal engine with two compression ratios, ensuring an energy supply to meet the consumption needs of an electric motor providing vehicle propulsion.

Claims

1. Management method (10) of a charge level (12) of an electric energy storage element (3) of a powertrain (1) of a hybrid motor vehicle, said powertrain (1) comprising at least one electric motor (2) driving the vehicle alone, at least one generator set (4) comprising a heat engine (5) driving an electric generator (6), the heat engine being able to operate at at least two compression ratios, the electric energy storage element (3) storing the electrical energy produced by the generator (6) and supplying the electric motor (2), the management method (10) controlling the heat engine (5) at a first compression ratio (15) or at a second compression ratio (16) depending on the level of charge (12) of the electrical energy storage element (3) and optionally on an electrical consumption (11) of the electric motor (2), characterised in that the heat engine (5) is maintained at the first compression ratio (15) when the level of charging (12) of the electrical energy storage element (3) is greater than a low state of charge threshold (13) and less than a high state of charge threshold (14), the high state of charge threshold (14) being greater than the low state of charge threshold (13), and the heat engine (5) is switched to the second compression ratio (16) which is the higher of the two compression ratios, when the level of charge (12) of the electrical energy storage element (3) is less than the low state of charge threshold (13).

2. Management method (10) according to claim 1, wherein the heat engine (5) is maintained at the second compression ratio (16) after the charge level (12) of the electric energy storage element becomes lower than the low state of charge threshold (13) and as long as the charge level (12) of the electric energy storage element (3) is lower than the high state of charge threshold (14), and the operation of the heat engine (5) is interrupted when the charge level (12) of the electric energy storage element (3) is higher than the high state of charge threshold (14).

3. Management method (10) according to claim 1 or 2, wherein the heat engine (5) is kept off as long as the charge level (12) of the electric energy storage element (3) is higher than the high state of charge threshold (14), and the heat engine (5) is turned on when the charge level (12) of the electric energy storage element (3) is lower than the high state of charge threshold (14).

4. Management method (10) according to any one of claims 1 to 3, wherein the low state of charge threshold (13) is between 5% and 60% of a maximum charge level of the electric energy storage element (3).

5. Management method (10) according to any one of claims 1 to 4, wherein the high state of charge threshold (14) is between 40% and 100% of a maximum charge level of the electric energy storage element (3).

6. Management method (10) according to any one of claims 1-5, controlling the heat engine (5) at the first compression ratio (15) or the second compression ratio (16) according to the power consumption of the electric motor (2), as long as the charge level (12) of the electric energy storage element (3) is lower than the high state of charge threshold (14) and higher than the low state of charge threshold (13).

7. Powertrain (1) for a hybrid motor vehicle, comprising at least one electric motor (2) driving the vehicle alone, at least one generator set (4) comprising a heat engine (5) driving an electric generator (6), the heat engine being able to operate at at least two compression ratios, an electric energy storage element (3) storing the electric energy produced by the generator (6) and powering the electric motor (2), characterised in that the powertrain further comprises a control module (8) configured to implement a method for managing (10) a charge level (12) of 1 electric energy storage element (3) according to any one of the preceding claims.

8. Powertrain (1) according to the preceding claim, wherein the heat engine (5) comprises a movable assembly (20) provided with at least one crankshaft (21), at least one piston (22) and at least one connecting rod (23) connecting the piston (22) to the crankshaft (21), said connecting rod (23) comprising a means (30) for adjusting a height of the piston (22) to operate the heat engine (5) at the first compression ratio (15) or at the second compression ratio (16).

9. Powertrain (1) according to the preceding claim, wherein the means (30) for adjusting the height of the piston (22) comprises at least one eccentric (31) which carries an axis of the piston (22) and whose position is controlled by two control members (32) carried by the connecting rod (23).

10. Motor vehicle comprising a powertrain (1) according to any one of claims 7 to 9.