Method for optimising the stabilised performance of a supercharged internal combustion engine under extreme conditions
Patent Information
- Application Number
- EP2023834247
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-01-11
- Filing Date
- 2023-12-04
- Publication Date
- 2025-11-19
AI Technical Summary
Supercharged gasoline internal combustion engines, particularly those using the Miller combustion cycle, face inefficiencies in extreme conditions such as high altitude and temperature due to reduced air density and filling, with current regulation lacking dedicated settings for stabilized performance.
A method for controlling the engine's intake and exhaust camshafts by calculating a target filling and comparing it to the maximum achievable filling, activating an optimum adjustment based on altitude and temperature to optimize camshaft phasing and enhance volumetric efficiency.
This approach improves engine torque and efficiency by adjusting camshaft settings to balance thermomechanical constraints, ensuring better performance in extreme conditions by optimizing air filling and reducing the impact of altitude and temperature variations.
Smart Images
Figure 1.1
Abstract
Description
DESCRIPTION TITLE: METHOD FOR OPTIMIZING THE STABILIZED PERFORMANCE UNDER EXTREME CONDITIONS OF A SUPERCHARGED INTERNAL COMBUSTION ENGINE
[0001] The present invention claims priority from French application No. 2300259 filed on 11.01.2023, the content of which (text, drawings and claims) is incorporated herein by reference.
[0002] The present invention relates to a method for optimizing the stabilized performance under extreme conditions of a supercharged internal combustion engine. The invention finds a particularly advantageous, but not exclusive, application with supercharged gasoline internal combustion engines implementing a "Miller" type combustion cycle.
[0003] As is well known, gasoline combustion engines can implement an "Atkinson" type combustion cycle in which the intake valve is closed after bottom dead center. These engines are robust at altitude and in hot temperature conditions. This type of engine can be equipped with different calibrations of camshaft phasers settings that can be activated depending on the living situations. For example, there is the possibility of calibrating specific settings favoring the engine dynamics, but there is no strategy to optimize the settings according to ambient conditions, such as temperature and pressure.
[0004] In order to reduce particulate emissions under new regulations, including the European €7, Sulev30 in the United States of America and China7 in China, a Miller-type combustion cycle has been adopted by some car manufacturers.
[0005] The Miller combustion cycle is based on the intake valve closing before bottom dead center. This type of combustion cycle impacts the internal combustion engine's breathing, as it drastically reduces the volumetric efficiency corresponding to the capacity to enclose a mass of air in the cylinder at a given pressure. As a result, engines using a Miller cycle require more boost pressure and therefore bring the engine closer to its thermomechanical constraints.
[0006] Figure 1 shows an architecture of a supercharged internal combustion engine comprising an internal combustion engine 10 supercharged by a turbocharger 11 comprising an air compressor 13 and a turbine 14. The air compressor 13 makes it possible to compress the intake air so as to optimize the filling of the cylinders of the internal combustion engine 10. For this purpose, the air compressor 13 is arranged on an intake duct 15 upstream of the internal combustion engine 10. The intake duct 15 also comprises an air inlet housing 16 receiving air from the outside (at ambient pressure and temperature) as well as an air filter 17. The intake duct 15 is connected to an intake distributor 18 capable of distributing the air in the cylinders of the internal combustion engine 10.
[0007] The flow of exhaust gases from the internal combustion engine 10 drives the turbine 14 arranged on an exhaust pipe 19 connected to an exhaust manifold 27 in rotation, causing the exhaust gases from the cylinders to converge towards the exhaust pipe 19. The turbine 14 then drives the air compressor 13 in rotation via a coupling shaft 20.
[0008] A discharge valve 28 associated with a discharge circuit 29 makes it possible to manage the quantity of exhaust gas circulating through the turbine 14 and consequently to regulate the rotation speed of said turbine 14. Certain turbines 14 may not be equipped with this device and regulate the rotation speed via internally arranged blades (variable geometry turbine).
[0009] A discharge valve 21 associated with a discharge circuit 22 makes it possible to secure the compressor 13 when the pressure at its terminals becomes too high by returning part of the flow supplied by the compressor 13 to the inlet of said compressor 13 via the discharge conduit 22.
[0010] In order to maximize the density of the air, a heat exchanger 23 called RAS (for "Supercharge Air Cooler") is used, capable of cooling the air circulating in the intake duct 15. The exchanger 23 is mounted downstream of the air compressor 13 and upstream of an air metering device 24 making it possible to manage a quantity of air entering the cylinders.
[0011] Furthermore, a catalyst 25, in particular a three-way type catalyst, is arranged on the exhaust pipe 19. The catalyst 25 may or may not be associated with a particulate filter.
[0012] The exhaust pipe 19 may also include other post-treatment systems not illustrated in FIG. 1, such as an ammonia reducer, a second particle filter, a second catalyst for example.
[0013] The exhaust pipe 19 also comprises at least one silencer 26.1, 26.2. In this case, an intermediate silencer 26.1 and a final silencer 26.2 are provided in order to comply with the noise standards of motor vehicles.
[0014] The intake pipe 15 and the exhaust pipe 19 as well as the elements arranged on these pipes 15, 19 form what is called the air loop in the remainder of the document.
[0015] Figure 2 illustrates the difference between a Miller combustion cycle (left) and an Atkinson combustion cycle (right). The following is a list of abbreviations in the figure: V: Volume Vmin: Compression volume Vh: Cylinder volume p pressure Patm: Atmospheric pressure BDC: "Bottom Dead Center" or bottom dead center in French TDC: "Top Dead Center" or top dead center in French CA: "Crank Angle" or crankshaft angle in French h: valve lift EVO: "Exhaust Valve Opening" EVC: "Exhaust Valve Closing" IVO: "Inlet Valve Opening" IVC: "Inlet Valve Closing" EIVC: "Early Inlet Valve Closing" LIVC: "Late Inlet Valve Closing" LCT: "Load control with throttle" or load control with the air meter, EIVC_P: EIVC Profile LIVC_P: LIVC's Profile Conv_P: Conventional profile Ech: Exhaust Adm: Admission
[0016] Figure 3 illustrates the impact of the millerization level on volumetric efficiency. The lower the intake closure value F_adm, the earlier the valve closes and consequently the millerization rate is higher. In this case, iso-lines are formed vertically.
[0017] The intake valve F_adm and exhaust valve F_ech closures are expressed in crankshaft degrees after bottom dead center.
[0018] The current regulation of the thermal engine makes it possible to optimize the camshaft settings during a transient phase, i.e. when a current value of air filling of the cylinders evolves towards a set value of air filling of the cylinders.
[0019] However, for a stabilized performance of the internal combustion engine, i.e. when a current value of a cylinder air filling is close to or equal to a set value of a cylinder air filling, there are no dedicated settings. As a result, the operation of a current engine is less efficient in extreme conditions, i.e. at a high altitude at which the air density and the cylinder filling decrease and / or at a high temperature.
[0020] The invention aims to effectively remedy this drawback by proposing a method for controlling a supercharged gasoline internal combustion engine comprising an intake camshaft and / or an exhaust camshaft comprising: - a step of calculating a setpoint filling by selecting the minimum between a setpoint filling before limitation and a maximum filling under the constraint of self-ignition of a combustion, - a comparison step between the target filling and a maximum filling that the internal combustion engine can achieve with initial intake and / or exhaust camshaft settings, and - if the target filling is greater than the maximum filling that the internal combustion engine can achieve with the initial settings, said method also comprises: - a step of activating an optimum adjustment of intake and / or exhaust camshafts depending on an altitude and / or an outside temperature.
[0021] According to one implementation of the invention, said method further comprises a step of prior verification that generic operating conditions of the internal combustion engine are met, before implementing the step of activating the optimum adjustment of intake and / or exhaust camshafts.
[0022] According to one implementation of the invention, the generic operating conditions of the internal combustion engine relate to a temperature of a coolant, above a threshold temperature or within a predetermined temperature range, and / or to a speed of the internal combustion engine within a predetermined speed range.
[0023] According to an implementation of the invention, said method further comprises a step of verifying that a transient optimization strategy impacting an adjustment of the intake and / or exhaust camshafts is not already activated before implementing the step of activating the optimum adjustment of the intake and / or exhaust camshafts.
[0024] The invention also relates to a control computer for a supercharged gasoline internal combustion engine comprising an intake camshaft and / or an exhaust camshaft, characterized in that said computer is configured: - to calculate the setpoint filling by selecting the minimum between a setpoint filling before limitation and a maximum filling under the constraint of self-ignition of a combustion, - to make a comparison between a target filling and a maximum filling that the internal combustion engine can achieve with initial intake and / or exhaust camshaft settings, and - if the target filling is higher than the maximum filling that the internal combustion engine can achieve with the initial settings, - to activate optimum adjustment of intake and / or exhaust camshafts depending on altitude and / or outside temperature.
[0025] According to one embodiment of the invention, said calculator is configured to verify that generic operating conditions of the internal combustion engine are met, before implementing the step of activating the optimum adjustment of intake and / or exhaust camshafts.
[0026] According to one embodiment of the invention, the generic operating conditions of the internal combustion engine relate to a temperature of a coolant, higher than a threshold temperature or within a predetermined temperature range, and / or to a speed of the internal combustion engine within a predetermined speed range.
[0027] According to one embodiment of the invention, said computer is configured to verify that a transient optimization strategy impacting an adjustment of the intake and / or exhaust camshafts is not already activated before implementing the step of activating the optimum adjustment of the intake and / or exhaust camshafts.
[0028] The invention further relates to a motor vehicle comprising a computer as defined above.
[0029] According to one embodiment of the invention, said motor vehicle comprises a supercharged gasoline internal combustion engine.
[0030] The invention will be better understood by reading the following description and examining the accompanying figures. These figures are given only for illustrative purposes but in no way limit the invention.
[0031] [Fig. 1], already described, shows an architecture of a supercharged internal combustion engine implementing the method according to the present invention;
[0032] [Fig. 2], already described, illustrates Miller (left) and Atkinson (right) type combustion cycles;
[0033] [Fig. 3], already described, illustrates the influence of a "millerization" rate on the volumetric efficiency of the internal combustion engine;
[0034] [Fig. 4] illustrates the impact of altitude on the performance of a supercharged gasoline internal combustion engine;
[0035] [Fig. 5] illustrates the engine behavior with respect to air loop constraints and combustion limits;
[0036] [Fig. 6] illustrates the impact of temperature on the performance of a supercharged gasoline internal combustion engine;
[0037] [Fig. 7] is a graph of cylinder air filling versus intake valve closing time illustrating the impact of temperature on the performance of a supercharged gasoline internal combustion engine;
[0038] [Fig. 8] illustrates the positioning of the intake and exhaust camshaft settings optimizing performance as a function of filling for two speeds of the supercharged gasoline thermal engine;
[0039] [Fig. 9] illustrates a principle of management of the phasing of the intake and exhaust camshafts according to the invention;
[0040] [Fig. 10] illustrates functional blocks for activating a specific adjustment of camshafts in stabilized mode and in extreme conditions according to the invention;
[0041] [Fig. 11] illustrates a first variant of the functional blocks of Figure 10;
[0042] [Fig. 12] illustrates a second variant of the functional blocks of Figure 10;
[0043] [Fig. 13] illustrates a third variant of the functional blocks of Figure 10.
[0044] Figure 4 illustrates the impact of altitude on the performance of the thermal engine 10. For each graph, the evolution of the torque is illustrated as a function of the intake valve closing times F_adm and the exhaust valve closing times F_ech. The stars illustrate the setting optimizing the torque. The dotted lines illustrate the boundaries of the different constraints. With the altitude, these boundaries evolve. With the initial setting, the compromise of constraints is no longer valid at altitude, the thermal engine 10 then has more margin at the initial constraint. The adjustment of the camshaft phase shifters is therefore not optimal. Here with the altitude, the compromise of constraints is much more accentuated on the supercharging part, leaving margin on the combustion part.It is then necessary to delay the closing of the intake valve, thereby reducing the millerization rate and allowing better volumetric efficiency of the internal combustion engine 10. With this new setting, the engine torque is greater than if the initial setting had been retained.
[0045] Figure 5 illustrates the behavior of engine 10 with respect to the constraints of the air loop Lim_BA (maximum turbocharger speed, air compressor outlet temperature 13, compressor surge) and the combustion limits Lim_COMB (knocking, "rumble" or roar in French, exhaust temperature). The filling Remp on the ordinate is indicated as a function of the intake valve closing times F_adm on the abscissa. The line Remp_CC corresponds to the filling to be reached to obtain the torque target. The effect of altitude means that the thermal engine 10 arrives more quickly within the limits of the air loop Lim_BA.If the optimal setting at 0 m (white dotted star E0) is maintained at altitude then the maximum filling (capacity of the engine to enclose a mass of air in the cylinder compared to a theoretical air mass) achievable is then limited by the air loop (grey star E1) and in this case, the heat engine 10 moves away from the combustion constraints. With the invention, the compromise between the limits of the air loop Lim_BA and the combustion limits Lim_COMB is. found modified to move to the black star E2 allowing to have a more important filling and consequently a more important torque.
[0046] Figure 6 illustrates the impact of temperature on the performance of the supercharged internal combustion engine. For each graph, the evolution of the torque is illustrated as a function of the closing times of the intake valves F_adm on the ordinate and of the exhaust valves F_ech on the abscissa. The stars illustrate the setting optimizing the torque. The dotted lines illustrate the boundaries of the different constraints. The increase in ambient temperature (and consequently of the temperature in the intake manifold 18) does not impact the optimal settings. Indeed, there are two opposing effects. The ambient temperature effect alone will tend to limit the thermal engine 10 on an air loop constraint (such as the outlet temperature of the air compressor 13) and therefore to favor a setting with a rather late closing of the intake valves.Conversely, the effect of the temperature of the intake manifold 18 alone will tend to limit the thermal engine 10 on a combustion constraint and therefore to favor an adjustment with an early closing of the intake valves.
[0047] Figure 7 illustrates the phenomenon previously mentioned regarding the two air temperatures. The reference setting is illustrated by the white star PO. In the case where only the ambient air temperature increases but the temperature in the intake manifold 18 remains the same, then the outlet temperature of the air compressor 13 increases and the internal combustion engine 10 reaches an air loop constraint. If the intake valve closing settings are maintained then the drop in performance is experienced (see star P1). A later closing of the intake valves makes it possible to follow the trend at the limit of the air loop to allow returning as close as possible to the target torque (see star P2). In the case where only the temperature of the intake manifold 18 increases, the internal combustion engine 10 is able to compensate until reaching the combustion constraint (see star P3).Earlier closing of the intake valves allows. to increase this margin and therefore make the performance more robust (see star P4). In the case where the two temperatures vary at the same time, the compromise remains almost identical (see star P5)
[0048] The impacts of altitude and outside temperature illustrated in Figures 4 to 7 show the benefit of dedicating specific camshaft phasing in order to maximize performance in the degraded conditions of engines equipped with a "Miller" type combustion system.
[0049] Figure 8 illustrates the positioning of the intake and exhaust camshaft settings optimizing performance as a function of the filling Remp for two engine speeds of the thermal engine 10. O_adm corresponds to the opening of the intake valves expressed in crankshaft degrees and F_ech corresponds to the closing of the intake valves expressed in crankshaft degrees. It is possible to create a single profile per speed allowing the settings optimizing the performance of the internal combustion engine 10 to be indexed as a function of the filling.
[0050] Figure 9 illustrates in block diagram form the impact of the invention on the control of the intake and / or exhaust camshafts already existing in the control computer. Blocks (1) to (n) correspond to predefined settings of the intake and / or exhaust camshafts. Input (a) is a Boolean which represents the need to activate the setting (1). Inputs (0) to (Q) represent the Booleans for activating the settings (2) to (n). Block B1 is a setting prioritization block. Indeed, if several inputs are requested, block B1 makes it possible to choose which of them has the highest priority and sends the prioritized information to block B2. Block B2 makes it possible to select the final setting to be applied (r) from among the different predefined settings.
[0051] Among the many predefined settings, some were not used. The invention is based on this assumption. Indeed, one of the unused settings was diverted so as to be able to enter the settings there optimal in degraded conditions. Consequently, the input of block B1 associated with the new setting is modified.
[0052] For convenience, the setting that optimizes performance in degraded conditions is defined as block (2). The input of block B1 associated with the settings of block (2) is input (0).
[0053] Figure 10 illustrates in block diagram form the architecture according to the invention for creating the activation criterion (0) of a specific adjustment of the intake and exhaust camshafts. According to this adjustment, the intake valves are closed later than in the context of a conventional Miller-type operation. By "adjustment of the camshafts" is meant an adjustment of the phase shifters of the intake and exhaust camshafts. This specific adjustment is an optimum adjustment of the intake and exhaust camshafts depending on an altitude and / or an outside temperature. The different blocks are implemented in software by a computer 30 of the motor vehicle (see Figure 1).
[0054] Block (1') allows the calculation of the setpoint filling (c) by selecting the minimum between the setpoint filling before limitation (a) and the maximum filling under the constraint of self-ignition of a combustion (b). The setpoint filling before limitation (a) is a setpoint air filling of the cylinders determined without taking into account the air filling limits linked to the current operation of the engine. These limits can be, for example, a function of a maximum speed of the turbocharger 11, a maximum temperature at the outlet of the air compressor 13, a pumping effect of the compressor 13, an exhaust gas temperature or a combustion stability. This setpoint filling before limitation (a) is the image of the driver's request without the feedback of what the engine can do. This notion of limitation is still commonly referred to as saturation or limitation in the field of motor control.
[0055] The maximum filling under self-ignition constraint of a combustion (b) takes into account constraints linked to a phenomenon of knocking in which uncontrolled combustion of gases is observed in the chamber of a cylinder after the spark or the phenomenon of "rumble" in which uncontrolled combustion of gases is observed in the chamber of a cylinder before the spark.
[0056] Block (2') checks that the setpoint filling (c) is greater than the maximum filling that motor 10 can do with the initial settings at the limit of the air loop (d) and returns a Boolean value (e), for example 1, if the check is true. Block (3') is an "AND" logic block which checks that all the input conditions (e), (f) and (g) are met and returns the Boolean value, for example 1 (0) in this case.
[0057] Input (f) checks that a transient optimization is not already activated in order to avoid double activation of camshaft adjustments. Transient optimization corresponds to a camshaft adjustment implemented when the current cylinder air filling value tends towards a target value far from the current value.
[0058] Input (g) is a pre-check that all generic conditions are met, namely that the internal combustion engine coolant temperature is above a threshold temperature of, for example, around 90 degrees Celsius or is within a predetermined temperature range, and / or that the engine speed is within a predetermined speed range.
[0059] According to a first implementation variant illustrated in Figure 11, there is no optimization of the engine dynamics. Consequently, input (f) is deleted. Block (1') allows the setpoint filling (c) to be calculated by selecting the minimum between the setpoint filling before limitation (a) and the maximum filling under the constraint of self-ignition of a combustion (b). Block (2') verifies that the setpoint filling (c) is greater than the maximum filling that the engine can do with the initial settings (d) and reference 1 (e) if the check is true. Block (3') is an "AND" logic block that checks that all input conditions (e), (f) and (g) are met and returns the value 1 (0) in this case. Input (g) is a pre-check that all generic conditions are met (water temperature, engine speed, or other).
[0060] According to a second implementation variant illustrated in Figure 12, the generic conditions (g) are also removed, so that block (3') no longer has any reason to exist. Block (1') makes it possible to calculate the setpoint filling (c) by selecting the minimum between the setpoint filling before limitation (a) and the maximum filling under the constraint of self-ignition of a combustion (b). Block (2') verifies that the setpoint filling (c) is greater than the maximum filling that the engine 10 can do with the initial settings (d) and return 1 (P) if the verification is true.
[0061] According to a third implementation variant illustrated in Figure 13, the setpoint filling is not limited by the combustion constraints (b). In this case, it is a simple comparison between the setpoint filling (a) and the maximum filling achievable by the engine (d). Consequently, block (T) no longer exists. Block (2') checks that the setpoint filling before limitation (a) is greater than the maximum filling that the engine 10 can achieve with the initial settings (d) and return 1 (P) if the check is true.
[0062] Other variants resulting from the combination of the previous variants can be implemented.
Claims
CLAIMS 1. Method for controlling a supercharged gasoline internal combustion engine (10) comprising an intake camshaft and / or an exhaust camshaft, characterized in that said method comprises: - a step of calculating a setpoint filling (c) by selecting the minimum between a setpoint filling before limitation (a) and a maximum filling under the constraint of self-ignition of a combustion (b), - a comparison step between the target filling (c) and a maximum filling that the internal combustion engine (10) can achieve with initial intake and / or exhaust camshaft settings, and - if the set filling (c) is greater than the maximum filling that the internal combustion engine (10) can achieve with the initial settings (d), said method further comprises: - a step of activating an optimum adjustment of intake and / or exhaust camshafts depending on an altitude and / or an outside temperature.
2. Method according to claim 1, characterized in that it further comprises a step of prior verification that generic operating conditions (g) of the internal combustion engine (10) are met, before implementing the step of activating the optimum adjustment of intake and / or exhaust camshafts.
3. Method according to claim 2, characterized in that the generic operating conditions of the internal combustion engine (10) relate to a temperature of a coolant, higher than a threshold temperature or within a predetermined temperature range, and / or to a speed of the internal combustion engine (10) within a predetermined speed range.
4. Method according to any one of claims 1 to 3, characterized in that it further comprises a step of verifying that a transient optimization strategy (f) impacting an adjustment of the intake camshafts and / or exhaust is not already activated before implementing the step of activating the optimum adjustment of intake and / or exhaust camshafts.
5. Computer (30) for controlling a supercharged gasoline internal combustion engine (10) comprising an intake camshaft and / or an exhaust camshaft, characterized in that said computer (30) is configured - to calculate the setpoint filling (c) by selecting the minimum between a setpoint filling before limitation (a) and a maximum filling under the constraint of self-ignition of a combustion (b), - to make a comparison between a target filling and a maximum filling that the internal combustion engine (10) can achieve with initial intake and / or exhaust camshaft settings, and - if the set filling (c) is greater than the maximum filling that the internal combustion engine (10) can achieve with the initial settings (d), - to activate optimum adjustment of intake and / or exhaust camshafts depending on altitude and / or outside temperature.
6. Calculator according to claim 5, characterized in that it is configured to verify that generic operating conditions (g) of the internal combustion engine (10) are met, before implementing the step of activating the optimum adjustment of intake and / or exhaust camshafts.
7. Calculator according to claim 6, characterized in that the generic operating conditions of the internal combustion engine (10) relate to a temperature of a coolant, higher than a threshold temperature or within a predetermined temperature range, and / or to a speed of the internal combustion engine (10) within a predetermined speed range.
8. Calculator according to any one of claims 5 to 7, characterized in that it is configured to verify that a transient optimization strategy (f) impacting an intake and / or exhaust camshaft adjustment is not already activated before implementing the step of activating the optimum intake and / or exhaust camshaft adjustment.
9. Motor vehicle comprising a computer (30) according to any one of claims 5 to 8.
10. Motor vehicle according to claim 9, characterized in that it comprises a supercharged gasoline internal combustion engine (10).