METHOD FOR DETERMINING THE CONTROL SETPOINT OF A TURBOCHARGER TURBINE, VEHICLE AND PROGRAM BASED ON SUCH A METHOD

Abstract

The invention relates to a method for determining a final setpoint for a characteristic quantity of the opening of a turbocharger turbine equipping an internal combustion engine during a transient phase of engine torque build-up. The final setpoint is determined by means of an intake pressure and a de-sizing step. The method is characterized in that the intake pressure during the de-sizing step is calibrated between a reference pressure (1), an ambient pressure (2), and an engine boost pressure (3). The invention also relates to a program and a vehicle based on such a method. Figure 3

Description

Title of the invention: METHOD FOR DETERMINING TURBOCOM TURBINE CONTROL SETPOINT PRESSER, VEHICLE AND PROGRAM BASED ON SUCH A METHOD

[0001] The invention relates to the field of controlling the supercharging systems of internal combustion engines. This invention relates to a method for determining a final setpoint of a quantity characteristic of the opening of a turbocharger turbine.

[0002] The current state-of-the-art solution is described in patent WO2022 / 084596 A1 which consists of determining a final turbine opening setpoint during the transient torque increase phase.

[0003] The state-of-the-art solution showed some limitations during the calibration phase of the Euro 6.4 generations. Indeed, several blocks described in the state-of-the-art had to be reworked in order to take into account different issues.

[0004] These include: - a problem with the establishment of the initial intake pressure not working completely as expected; - a problem of precision of the final position instruction in the case of a specific mode of protection against the phenomenon of abnormal combustion (called "rumble" in English or LSPI) which occurs before the controlled and uncontrolled ignition creating very high pressures in the combustion chamber and which can be destructive for the engine; - a problem of flexibility in the mapping of the limitation associated with the specific mode known as performance; - a need to add a securing device for the turbine opening position dependent on external conditions.

[0005] The objective of the invention is to develop a limitation of the position setpoint of the actuator of a variable geometry turbocharger making it possible to optimize the transient torque phases of an internal combustion engine. More specifically, the invention makes it possible to develop a limitation of the turbine upstream pressure setpoint making it possible to maximize the transient engine torque. The latter is then translated into the position of the turbocharger blades using the inverse turbine model.

[0006] To achieve this objective, the invention proposes a method for determining a final setpoint of a quantity characteristic of the opening of a turbocharger turbine equipping an internal combustion engine during a transient phase of engine torque increase, the final setpoint being determined by means of an intake pressure and a scaling step, characterized in that the intake pressure during the sizing step is calibratable between a reference pressure; an ambient pressure; and an engine boost pressure to obtain a selected intake pressure.

[0007] By "dimensioning" is meant a partial or total removal of the units of an equation by an appropriate substitution of variables, with the aim of simplifying the parametric representation of physical problems.

[0008] Advantageously, the invention is based on the state of the art and proposes solutions for correcting the limitations of the state of the art observed during the development phase. This solution will improve the robustness of the turbine position but also provide more flexibility in the development for the calibration teams.

[0009] According to a variant, the engine comprises camshaft phase shifters and means for managing these phase shifters, and at least two specific modes for managing these phase shifters, and for each specific mode a calibration step by a calibration map, of the maximum admissible pressure upstream of the turbine dimensioned by the selected intake pressure, the maximum admissible pressure upstream of the turbine then being selected as a function of the specific mode.

[0010] The maximum admissible pressure represents the maximum pressure upstream of the turbine before the dreaded phenomenon appears (i.e. excessive pressure in the exhaust manifold consequently reducing the air filling of the engine).

[0011] This makes it possible to improve the accuracy of the final position setpoint.

[0012] According to a variant, the determination method comprises a step of determining a turbine upstream pressure comprising an application of a corrective factor by a corrective map as a function of the speed and the crossover, and an application of an offset map representing an offset of turbine upstream pressure as a function of the speed and the engine load.

[0013] This allows for improved flexibility in calibration as well as a fallback solution if the initial approach is complicated to calibrate.

[0014] According to a variant, the determination method comprises a step of determining a maximum turbine position as a function of a turbine position map, an engine speed and an engine load.

[0015] This makes it possible to secure the process by having a maximum and a minimum turbine position.

[0016] According to a variant, the determination method comprises a correction step of a turbine position as a function of altitude and ambient temperatures, by means of correction maps depending on engine speed and ambient pressure for one, and engine speed and ambient temperature for the other.

[0017] This makes it possible to calibrate a minimum turbine position directly as a function of the speed.

[0018] Another subject of the invention relates to a computer program comprising program code instructions for executing the steps of the control method according to the invention, when said program operates on a computer.

[0019] The invention further relates to a motor vehicle comprising an internal combustion engine supercharged by a turbocharger, characterized in that it comprises a computer comprising the means of acquisition, of processing by software instructions stored in a memory as well as the means of control of implementation of a method according to the invention.

[0020] According to a variant, the calculator comprises a dimensioning means for determining the final setpoint by means of an intake pressure, characterized in that the intake pressure is calibratable between a reference pressure; an ambient pressure; and an engine boost pressure to obtain a selected intake pressure.

[0021] According to a variant, the engine comprises camshaft phase shifters and means for managing these phase shifters, and at least two specific modes for managing these phase shifters, and for each specific mode a means for calibrating the admitted pressure by a calibration map establishing a maximum admissible pressure upstream of the turbine dimensioned by the selected intake pressure, the maximum admissible pressure upstream of the turbine then being selected as a function of the specific mode.

[0022] According to a variant, the motor vehicle comprises a means for determining an upstream turbine pressure implementing an application of a corrective factor by a corrective map as a function of the speed and the crossover, and an application of an offset map representing an upstream turbine pressure offset as a function of the speed and the engine load.

[0023] Preferably, the motor vehicle comprises means for correcting a position of the turbine as a function of the altitude and ambient temperatures, using correction maps dependent on the engine speed and ambient pressure for one, and on the engine speed and ambient temperature for the other.

[0024] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates a method for determining the setpoint of order according to the prior art; - [Fig.2] schematically illustrates variations in initial intake pressures used for sizing in the state of the art in the event of valve crossing and the corresponding problems; - [Fig.3] schematically illustrates the choice of reference or supercharging intake pressures within the framework of the invention; - [Fig.4] schematically illustrates the method for determining the control setpoint according to the invention including the addition of a branch dedicated to the specific protection mode called “rumble”; - [Fig.5] schematically illustrates the implementation of the offset maps within the framework of the invention and correction depending on the speed and the crossing; - [Fig.6] schematically illustrates the use of turbine position mapping and corrections based on altitude and ambient temperature; - [Fig.7] schematically illustrates an overview of the determination method according to the invention.

[0025] The invention relates to an improvement of the method of the co-pending application WO2022 / 084596 A1.

[0026] In order to correct the various sources of problems cited above, the applicant made the following modifications:

[0027] First, a replacement of the initial intake pressure by a choice between several adimensioning pressures. Indeed, by taking into account the ambient pressure, we take into account the impact of the altitude, by taking a reference pressure defined during the calibration phase, we always adimension the pressure by a constant that we can possibly set to 1 to cancel the adimensioning.

[0028] Finally, by taking the natural boost pressure (intake manifold pressure when the turbine and the throttle are fully open), we can only distinguish the pressure requirement when the engine is operating in the supercharged zone (use of the turbocharger). A choice can then be made so that we can select the pressure to be used during the tuning phase.

[0029] With this addition, the problem related to the initial intake pressure is solved and flexibility is provided for the calibration teams.

[0030] To answer the question of precision of the final position instruction, the applicant duplicated the approach dedicated to the performance mode for the so-called “rumble” protection mode. It is therefore a mixture between two embodiments of the co-pending application WO2022 / 084596 A1.

[0031] Indeed, when the motor operates in this protection mode, significantly crossed phase shifter positions are applied making the motor very sensitive to exhaust pressure. With the initial approach, the applicant was unable to provide the necessary precision, thus reducing the accuracy of the regulation and the engine's potential. This correction therefore provides robustness and helps avoid excessive exhaust pressure phenomena in this particular mode.

[0032] Concerning flexibility, in the state-of-the-art solution, the applicant had determined that for a specific engine mode, it would apply a simplified approach (performance mode). However, for more flexibility, after calibration, the applicant realized that it would be wise to add a corrective factor taking into account the engine speed as well as the valve crossover (the moment when the valves are open at the same time; we will speak of positive crossover when both valves are open, and negative crossover when both valves never open at the same time). In addition, the applicant also wants to add a possibility of simply having an offset relative to the intake pressure. With these additions, the applicant offers more flexibility in the calibration as well as a fallback solution if the initial approach is complicated to calibrate.

[0033] Concerning the safety, in the initial state-of-the-art solution, the maximum position of the turbine is calculated from the upstream turbine pressure. On the other hand, if one of the calibrations or the state-of-the-art solution does not work correctly (as observed during the development), the co-pending application WO2022 / 084596 A1 does not provide a fallback solution allowing the turbine position to be limited anyway. For this, the applicant proposes the addition of a final safety, between the calculation of the maximum turbine position and the set turbine position, which makes it possible to calibrate a minimum turbine position directly as a function of the speed. This position can be corrected as a function of the engine speed, the altitude and the ambient temperature.

[0034] Thus, the invention makes it possible to correct the problems observed with the state-of-the-art solution. By these developments, the applicant makes the calibration more robust, thus improving the operation of the engine, also making it easier, allowing a saving in calibration time.

[0035] [Fig. 1] illustrates the state of the art by taking into account several of its claims.

[0036] In fact, the establishment of the final instruction is the result of a maximum (54) between the maximum position optimizing the dynamics (Pos_max) and the set position established by another model (Cl).

[0037] The maximum position (Pos_max) is the result of a map (53) dependent on the exhaust flow rate (Qech) and the expansion ratio (Tdet) itself dependent on the maximum turbine upstream pressure (Pam_turb_max) and the turbine downstream pressure (Paval_turb).

[0038] The turbine upstream pressure is calculated in different ways and the choice of the inlet is done via block 62.

[0039] One way to calculate the turbine upstream pressure is illustrated in block Ml.

[0040] The second way to calculate the turbine upstream pressure is illustrated in block M2 and consists of calculating a maximum upstream turbine pressure (Pam_turb_max) taking into account the position of the camshaft phase shifters.

[0041] In the present invention, the state-of-the-art architecture can serve as a basis for the various developments presented.

[0042] If we take them in the order described above, concerning firstly the modification of the initial intake pressure used for dimensioning, during the development, the applicant noticed that the approach described in the state of the art which aims to dimension the intake pressure by an initial intake pressure (at the start of the transient phase) does not always work. Indeed, the initial approach only works correctly if the camshaft positions remain constant throughout the transient phase. As soon as the camshaft phase shifters evolve during the transient phase, dimensioning no longer works.

[0043] [Fig.2] illustrates the limitation observed during development in relation to the initial intake pressure. From [Fig.2], we understand the phenomenon observed during development.

[0044] The diagram above illustrates the valve crossover. When the crossover is negative (i.e. the valves never open at the same time) it is possible to accept more exhaust pressure since there is no risk of back flushing (return of exhaust gases to the intake) nor impact on the re-aspiration of exhaust gases (i.e. into the cylinder). Conversely, when the crossover is positive (i.e. the intake and exhaust valves are open at the same time) the engine is very sensitive to the exhaust pressure. Indeed, if it becomes too high compared to the pressures in the cylinder and at the intake, there may be the two phenomena described above (back flushing and / or re-aspiration) rapidly increasing the rate of residual gases (inert gases) in the chamber and thus preventing the cylinder from being properly filled with fresh air.

[0045] The lower diagram illustrates exhaust pressure as a function of intake pressure.

[0046] Curve 2a represents the optimal trajectory in the case of constant camshafts, curve 2d illustrates the optimal trajectory in the case where the camshafts evolve continuously so as to favor the dynamics of the engine. Curves 2a and 2d also represent the output of the exhaust pressure limitation model as described in patent application WO2022 / 084596 A1 with an initial intake pressure of the order of 1 bar.

[0047] Curves 2b and 2c represent the calculation of the current limitation model for constant camshafts in case the initial intake pressure is higher than 1 bar (for example: 1.2 bars and 1.6 bars).

[0048] Curves 2e and 2f represent the calculation of the current limitation model for camshafts that evolve continuously in the case where the initial intake pressure is greater than 1 bar (for example: 1.2 bars and 1.6 bars). These two curves illustrate the problem encountered in development since for a given intake pressure the output of the maximum turbine upstream pressure model is overestimated. This overestimation is visible throughout zone B of [Fig.2]. Zones A and C are well estimated since the camshafts no longer move in these zones.

[0049] Based on this observation, the applicant decided to change the inlet which serves as a dimensioning by replacing the initial admission pressure with a multiple choice between: - a reference pressure (1 bar for example); - ambient pressure, for example atmospheric pressure, which helps maintain the pressure ratio close as intake pressure and exhaust pressure change in the same way depending on altitude; and - natural boost pressure allowing the adimensioning to be activated only in the supercharged zone.

[0050] With this modification, the applicant adds flexibility for calibration by offering the possibility of choosing the optimal solution depending on the engine and its destinations.

[0051] [Fig.3] illustrates the new approach, block A allows a choice to be made between inputs 1 to 3 depending on the calibration 0 carried out during the development. Output 4 replaces the initial intake pressure.

[0052] The second evolution is directly linked to the architecture of the state of the art. We made the choice to allocate a model for estimating the maximum turbine upstream pressure for a mode which favors engine dynamics (block M1 of [Fig.l]) and to put all the other modes in a second approach. During the development, we encountered a precision problem on a particular mode (called anti-LSPI mode) which was integrated into the global approach of block M2 of [Fig.l].

[0053] Indeed, when this protection mode is activated, the camshaft phase shifters change positions, making the settings highly crossed. In addition, during this change of mode, the camshafts will evolve continuously with the load. Therefore, by favoring highly crossed settings, this mode makes the engine very sensitive to the upstream turbine pressure. Our initial approach, being a global approach, does not provide enough precision in predicting the maximum upstream turbine pressure. If an overestimation of the upstream turbine pressure is made, the plug phenomenon that we want to avoid will occur more quickly, making it less effective. the engine protection strategy. It is therefore necessary that the limitation of the upstream turbine pressure is as precise as possible when this mode is activated.

[0054] For this, we made a mixture between embodiments of the state of the art.

[0055] [Fig.4] illustrates the new approach. Indeed, blocks M1 and M2 as well as the Blocks 52, 53, 54 remain identical. We duplicate the approach of block M1 to create block M3 in which a specific calibration 70 is created for the anti LS PI mode. Therefore block 62 evolves a little.

[0056] The third development concerns the interior of block 61. Indeed, in the state of the art, the maximum turbine upstream pressure is directly linked to the intake pressure. In order to give more flexibility to the calibration teams, we have added a corrective factor at the outlet of block 61.

[0057] Block M1 was initially designed for a specific mode in which we knew the evolution profile of the camshaft phase shifters as a function of the intake pressure. However, during the project, the applicant realized that under certain conditions, it is necessary to evolve these camshaft positions via corrective factors. In this case, the camshaft position can be different for the same intake pressure. To overcome this problem, we propose to add a mapping dependent on the speed and the crossing of the camshaft phase shifters after block 61. With this evolution, we take this problem into account. Here we have taken block M1 as an example, but this evolution is also valid for block M3

[0058] A second approach allowing flexibility in the development consists of adding a final mapping of the P upstream turbine offset as a function of the engine speed and load. This development can be valid for the three blocks described in solution 2, M1, M2 and M3.

[0059] [Fig.5] illustrates the proposed developments. Map 80 represents the correction function of the speed (N) and the crossover (Cr). Map 90 represents the turbine upstream pressure offset function of the speed (N) and the engine load (Ld). Block 100 adds up the three inputs to establish the final turbine upstream pressure.

[0060] Concerning the securing of the maximum turbine position. Our solution consists of inserting between blocks 53 and 54 of the state of the art, a securing of the turbine position. The idea here is to be able to add a securing of the maximum turbine position by not using the upstream turbine pressure but by directly using the turbine position itself. We therefore establish a turbine position map as a function of the engine speed and the engine load. To deal with as many cases as possible, the turbine position must be corrected as a function of the altitude and ambient temperatures. For this we propose to add two other maps of correction dependent on engine speed and ambient pressure for the first, and on engine speed and ambient temperature for the second.

[0061] [Fig.6] illustrates our new approach. Indeed, block M4 represents the calculation of the maximum turbine position corrected as a function of atmospheric pressure Patm and ambient temperature Tadm for each engine speed N and each engine load Ld. Once this maximum turbine position has been calculated, we can determine a maximum between the maximum turbine position calculated via the state of the art and this new maximum position to determine a maximum secure position Pos_max_sec via block 110. The rest with block 54 remains identical to the state of the art.

[0062] [Fig.7] groups together all the developments of the proposed invention described above.

[0063] The invention further relates to a method and a corresponding control program. The program can be loaded into a controller of the motor vehicle.

Claims

Claims

1. Method for determining a final setpoint (Cf) of a characteristic magnitude of the opening of a turbocharger turbine equipping an internal combustion engine during a transient phase of torque increase of the engine, the final setpoint being determined by means of an intake pressure and a scaling step, characterized in that the intake pressure during the scaling step is calibratable between a reference pressure (1); an ambient pressure (2); and an engine boost pressure (3) to obtain a selected intake pressure.

2. Determination method according to claim 1, characterized in that the engine comprises camshaft phase shifters and means for managing these phase shifters, and at least two specific modes for managing these phase shifters (Ml), and for each specific mode a calibration step by a calibration map (60, 70), of the maximum admissible pressure upstream of the turbine asized by the selected intake pressure, the maximum admissible pressure upstream of the turbine (Pam_turb_max) then being selected (62) as a function of the specific mode.

3. Determination method according to any one of claims 1 to 2, characterized in that it comprises a step of determining a turbine upstream pressure comprising an application of a corrective factor by a corrective map (80) as a function of the speed (N) and the crossover (Cr), and an application of an offset map (90) representing an offset of turbine upstream pressure as a function of the speed (N) and the engine load (Ld).

4. Determination method according to any one of claims 1 to 3, characterized in that it comprises a step of determining a maximum turbine position as a function of a turbine position map, an engine speed and an engine load.

5. Determination method according to any one of claims 1 to 3, characterized in that it comprises a step of correcting a position of the turbine as a function of the altitude and ambient temperatures, by means of correction maps depending on the engine speed and ambient pressure for one, and on the engine speed and ambient temperature for the other.

6. A computer program comprising program code instructions for carrying out the steps of the control method according to any one of claims 1 to 5, when said program is running on a computer.

7. Motor vehicle comprising an internal combustion engine supercharged by a turbocharger, characterized in that it comprises a computer comprising the means of acquisition, processing by software instructions stored in a memory as well as the means of control of implementation of a method according to any one of claims 1 to 5.

8. Motor vehicle according to claim 7, characterized in that the computer comprises a dimensioning means for determining the final setpoint by means of an intake pressure, characterized in that the intake pressure is calibratable between a reference pressure (1); an ambient pressure (2); and an engine boost pressure (3) to obtain a selected intake pressure.

9. Motor vehicle according to any one of claims 7 to 8, characterized in that the engine comprises camshaft phase shifters and means for managing these phase shifters, and at least two specific modes for managing these phase shifters (Ml), and for each specific mode a means for calibrating the pressure admitted by a calibration map (60, 70) establishing a maximum admissible pressure upstream of the turbine asized by the selected intake pressure, the maximum admissible pressure upstream of the turbine (Pam_turb_max) then being selected (62) as a function of the specific mode.

10. Motor vehicle according to any one of claims 7 to 9, characterized in that it comprises a means for determining an upstream turbine pressure implementing an application of a corrective factor by a corrective map (80) as a function of the speed (N) and the crossover (Cr), and an application of an offset map (90) representing an upstream turbine pressure offset as a function of the speed (N) and the engine load (Ld).

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