Method for estimating the potential maximum load of a supercharged internal combustion engine
Patent Information
- Application Number
- EP2023834255
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-01-20
- Filing Date
- 2023-12-04
- Publication Date
- 2025-11-26
AI Technical Summary
Existing methods for estimating the maximum potential load of a turbocharged internal combustion engine are inaccurate, particularly in operating zones far from maximum potential, leading to errors up to 65% at low intake pressures, which can result in unnecessary electrical energy consumption and incorrect ESP system activation.
A method involving a calculation chain that iteratively determines the maximum compression ratio, compressor outlet pressure, intake distributor pressure, and load, using existing engine sensors and coefficients calculated from engine operating points, with additional processing loops to converge on accurate maximum load values.
Improves the precision of maximum load estimation, reducing errors and enhancing torque structure control and ESP system reliability, especially in hybrid vehicles, while being an economical software-based solution.
Smart Images
Figure FR2023051909_25072024_PF_FP_ABST
Abstract
Description
DESCRIPTION TITLE: METHOD FOR ESTIMATING THE MAXIMUM POTENTIAL LOAD OF A SUPERCHARGED INTERNAL COMBUSTION ENGINE The present invention claims priority from French application 2300528 filed on 20.01.2023, the content of which (text, drawings and claims) is incorporated herein by reference.
[0001] The field of the invention relates to a method for estimating the maximum potential load of a turbocharged internal combustion engine.
[0002] The use of turbocharging systems has become widespread in motor vehicles to minimize pollutant emissions. Among the software functions controlling a turbocharged engine, one is dedicated to continuously calculating the engine's maximum potential load. Load is defined as the ratio between the mass of air admitted into the cylinders and the maximum permissible air mass at the reference pressure of 1013 mbar. In the case of a turbocharged engine, the load is dependent on the turbocharger's operation.
[0003] For example, US patent document B2-9080506 describes a method for controlling a supercharged engine equipped with a spiral valve that can be used to provide the necessary turbine power to drive increased compressor recirculation via a compressor recirculation valve. By coordinating the action of the compressor and the spiral valve, this solution allows the use of a larger compressor and turbine, thereby increasing the compression ratio at low speeds. It aims to improve supercharging performance.
[0004] More specifically, a known maximum load calculation function involves a data processing chain that takes into account, in particular, a characteristic map called the compressor field, which provides values for the compression ratio between the compressor's outlet and inlet pressures. The maximum characteristic limit of this field defines the operating zone where the compressor is not active, known as the pumping zone. For example, the applicant has filed patent document FR-A1-2911371 describing a method for measuring the limit of Pumping from a compressor indicates these maximum compression ratio values. As taught in this document, this ratio is determined experimentally.
[0005] More specifically, known models for estimating the maximum load of a turbocharged turbocharged engine implement a calculation chain based on the characteristic curve of the compression ratio. Starting with a setpoint compressor flow rate, an initial step uses the compressor's pumping limit to establish the maximum value of the compression ratio. Then, using this ratio and a measurement or estimate of the compressor inlet pressure, a second step in the calculation chain provides an estimate of the compressor outlet pressure. From this latter value, a third step, based on the experimentally observed airflow during operation in the turbocharged zone of the engine between the compressor and the intake lines, allows for the recalculation of the pressure in the intake manifold.Finally, a fourth treatment based on a characteristic engine load equation allows us to establish the maximum load value as a function of the pressure in the intake distributor.
[0006] In operating areas furthest from the maximum potential, errors were observed in the estimation of the maximum load.
[0007] Figure 1 illustrates this situation on a compressor field map, with the compression ratio P2 / P1 represented on the y-axis, where P2 is the compressor outlet pressure and P1 the inlet pressure. This ratio can vary, for example, from 1 to 3.5 depending on the compressor's size. Compressor airflow values (Db) are shown. The compressor velocity lines (LVn) are also shown. Curve C1 is an iso-speed curve for the engine, indicating the compression ratio values as a function of the airflow. To the right of the slope break point is the compressor activation zone. The dashed line LP indicates the pumping limit, which corresponds to the maximum ratio values. The white area above this limit is the pumping zone. Point Rp1 represents the maximum ratio for the compressor's setpoint flow rate (DB0).According to the known estimation model, from this Rp1 value, a maximum load is estimated which is in fact that corresponding to the setpoint flow rate and not the maximum potential flow rate at constant operating conditions, which would be the ratio Rp2. The maximum errors of this model can reach up to 65% in the areas. Further from the engine's maximum potential are the low intake pressure zones, primarily between 2000 and 3000 rpm. Conversely, this model's estimation is quite accurate in the high pressure zones where the engine's potential is at its maximum.
[0008] This error can be detrimental when the ESP (Electronic Stability Program) system is activated. In particular, if the potential maximum load information is underestimated, in the case of a hybrid powertrain, the torque structure strategies may call for electric motor torque to compensate for a lack of torque from the internal combustion engine, even when this is not actually necessary. This results in increased electrical energy consumption. Furthermore, the illumination of the ESP warning light depends on the difference between the load requested by the ESP and the estimated maximum engine load. If this estimate is too low, the warning light may not illuminate even though the ESP is intervening.
[0009] One objective of the invention is to overcome the aforementioned problems. The invention aims to improve the accuracy of the function estimating the potential maximum load value of a turbocharged internal combustion engine. Another objective is to provide an improved, low-cost estimation solution. A further objective is to improve the control of the torque structure function by delivering a more accurate estimate of the engine's maximum load.
[0010] More specifically, the invention relates to a method for estimating the maximum potential load of a turbocharged internal combustion engine implementing a calculation chain comprising the following successive steps:
[0011] - Determining the maximum compression ratio of a compressor as a function of a parameter representative of the compressor's flow rate,
[0012] - Determining the maximum pressure at the compressor outlet as a function of the maximum compression ratio,
[0013] - Determining a maximum pressure in the intake manifold based on the maximum pressure at the compressor outlet,
[0014] - Determining the maximum load based on the maximum pressure in the intake distributor.
[0015] According to the invention, the calculation chain further includes the determination of a maximum compressor flow rate corresponding to the maximum load and a looping of the calculation chain by the maximum flow rate to determine a new value of the maximum load from at least a second processing loop of the calculation chain.
[0016] The method according to the invention may include the following additional features, alone or in combination:
[0017] - successive values of the maximum load are recalculated from processing loops of the calculation chain taking as input the last value of maximum flow rate until a convergence is detected between two values of maximum load from two successive processing loops of the calculation chain;
[0018] - the determination of the maximum compression ratio is determined from a mapping of the maximum compression ratio of a compressor field taking into account compressor flow values;
[0019] - the determination of the maximum pressure at the compressor outlet as a function of the maximum compression ratio is determined from an estimate or instantaneous measurement of the pressure at the compressor inlet;
[0020] - the determination of the maximum pressure in the intake distributor is calculated from a pressure difference between the compressor and the engine intake lines, in which the pressure difference is obtained by a mapping taking as input a measurement or estimate of the instantaneous flow rate of the turbocharger;
[0021] - the determination of the maximum load is calculated from a load equation according to the following relationship: Cmax = A*P2”max + B, where Cmax is the maximum load, P2”max is the maximum pressure in the intake distributor, A is a filling coefficient and B is a shift coefficient, where the coefficients A and B are calculated according to a mapping taking engine operating points as input;
[0022] - the determination of the maximum flow rate is calculated according to the following relationship: DBmax=Cmax*K, where DBmax is the maximum flow rate, K is a coefficient delivered by a mapping taking as input the instantaneous engine speed and Cmax is the maximum load;
[0023] The invention envisages a control unit of an internal combustion engine configured for the implementation of any of the embodiments of the method for estimating the maximum potential load of the engine according to the invention.
[0024] We also envision a computer program comprising instructions which, when the program is executed by a control unit of an internal combustion engine, cause the latter to implement any one of the embodiments of the method for estimating the maximum potential load of the engine.
[0025] We are also considering a motor vehicle with a turbocharged internal combustion engine controlled by such a control unit.
[0026] The invention offers the advantage of being an economical solution for improving the accuracy of the engine's maximum potential load, as it relies on a software processing chain based on the engine's existing sensors. The invention also improves the torque structure function, particularly when an ESP system is activated.
[0027] Other features and advantages of the present invention will become more apparent upon reading the following detailed description, which includes embodiments of the invention given by way of non-limiting examples and illustrated by the accompanying drawings, in which:
[0028] [Fig.1] represents a graph of a compressor field allowing the determination of a maximum compressor compression ratio as a function of a compressor setpoint flow value.
[0029] [Fig.2] schematically represents a block diagram of the calculation chain implemented by a function for estimating the maximum potential load of a turbocharged internal combustion engine according to the invention.
[0030] [Fig.3] represents a graph of a compressor field illustrating the search for the maximum compressor flow rate at iso-engine speed allowing to determine a maximum potential compression ratio of the compressor.
[0031] The invention applies to vehicles comprising a powertrain equipped with a turbocharged multi-cylinder internal combustion engine. It concerns vehicles with internal combustion or hybrid engines. The turbocharger can be... Fixed geometry, variable geometry with multiple vanes, or a slide-spool turbocharger. A turbocharger's function is to compress the intake air necessary for fuel combustion in order to increase the amount of air entering the cylinders and thus increase engine torque and power. The mechanical components of a turbocharger consist primarily of a turbine, a compressor, and a shaft mounted on a main bearing.
[0032] The engine control function includes means for acquiring, measuring, and estimating engine and turbocharger parameters, enabling the implementation of the maximum load estimation method according to the invention. These parameters include the compressor setpoint flow rate, engine speed, upstream temperature of the compressor, compressor field strength, and engine flow rate as a function of engine load. The maximum load parameter is particularly important for controlling the torque structure of a powertrain, which influences the various torque providers as well as human-machine interface elements, such as the ESP activation indicators.It should be noted that the maximum engine load is defined as the ratio between the maximum air mass that can be admitted into the cylinders, taking into account the operating limitations of the turbocharger and engine and their specific characteristics known on the test bench, and the maximum permissible air mass at the reference pressure of 1013 mbar. The invention aims to improve the accuracy of the maximum load estimation.
[0033] The control unit of an internal combustion engine is equipped with an integrated circuit computer and electronic memory, the computer and memory being configured to perform the maximum load estimation process. However, this is not mandatory. The computer could be external to the control unit, while still being coupled to it. In this latter case, it could itself be configured as a dedicated computer, possibly including dedicated software. Consequently, the control unit, according to the invention, can be implemented as software modules, electronic circuits, or hardware, or a combination of electronic circuits and software modules.
[0034] Figure 2 illustrates the implementation of the estimation process using a calculation chain E1, E2, E3, E4, and E5, which performs a data processing loop. The estimation function is triggered at the initialization of the motor control unit and continuously reiterates the calculations, for example every 10 milliseconds, during its operation.
[0035] The method comprises a first module E1 that determines the maximum compression ratio D2 of a compressor as a function of a parameter D1 representing the compressor flow rate according to the estimation method. This parameter D1 is a setpoint flow rate value for the turbocharger. Parameter D1 is continuously calculated by the turbocharger control unit. Module E1 determines, from the compressor field recorded as a map in the engine control unit's memory, a maximum value D2 of the compression ratio corresponding to the pumping limit. The compressor flow rate is a reduced flow rate that can be defined by a proportionality coefficient relative to the actual engine flow rate, for example, according to the following relationship:
[0036] [Math]:
[0038] Where, Qred is the reduced compressor flow rate, Q is the actual engine flow rate, T1 is the temperature upstream of the compressor, and P1 is the pressure upstream of the compressor.
[0039] Next, the calculation chain includes the second calculation module E2 which allows estimating, according to the estimation method, based on the maximum value of the ratio D2 and the value D3 measured or estimated pressure P1 at the compressor inlet, the value D4 of maximum pressure at the compressor outlet.
[0040] The calculation chain also includes a third calculation module, E3, which, according to the estimation method, estimates a maximum pressure value, D6, in the intake manifold based on the maximum pressure value D4 at the compressor outlet and a negative pressure difference D5 induced by the airflow between the compressor and the intake manifold. The value D5 was determined experimentally on a test bench and can be determined at any time from a map or model, assuming the engine is operating in the turbocharged zone with the throttle open.
[0041] Next, the calculation chain includes a fourth module E4 for the maximum load D9 as a function of the maximum pressure value D6 in the intake manifold. More precisely, according to the estimation method, the maximum load is calculated from a load equation based on the following relationship: Cmax = A*P2”max + B, where Cmax is the maximum load value D9, P2”max is an estimate of the pressure in the intake manifold, A is a filling coefficient corresponding to the value D7 in Figure 2, and B is a shift coefficient corresponding to the value D8 in the same figure. The values D7 and D8 are calculated based on functions, maps, or models known experimentally, taking as input engine operating points, including engine speed and camshaft phaser position.The load equation is a function configured in the control unit, well known to those skilled in the art in the field of internal combustion engine design and calibration.
[0042] The maximum motor load D9 is calculated by executing the first processing loop for the compressor's setpoint flow rate, which, in certain motor operating ranges, can differ significantly from the motor's maximum flow rate. This situation can lead to an error of approximately 65% of the maximum load value.
[0043] According to the invention, the method implements additional iterative loops of the calculation chain E1, E2, E3, and E4 by recalculating, using a fifth calculation module E5, a value D10 of the maximum compressor flow rate corresponding to the value D9 of the maximum load of the last processing loop. The value D10 is calculated according to the following relationship: DBmax = Cmax * K, where DBmax is the maximum flow rate, K is a proportionality coefficient provided by a map that takes the instantaneous engine speed as input, and Cmax is the last maximum load value calculated by module E4. The map is stored in the memory of the control unit and obtained experimentally during engine design.
[0044] Processing loops of the calculation chain for modules E1, E2, E3, E4, and E5 are iterated, taking as input to function E1 the value D10 calculated by the previous loop. These processing loops are repeated until the maximum charge value D9 converges to a value of the potential maximum charge. It has been observed that three or four iterative loops are sufficient, resulting in a time of 30 milliseconds or 40 milliseconds. milliseconds to obtain the potential maximum load value corresponding to the engine's potential maximum flow rate at constant speed. The accuracy of the maximum load estimation function is improved, which consequently enhances engine control functions dependent on the potential maximum load value, including the torque structure function, the intervention decisions of an electric drive machine in the case of a hybrid vehicle, and also the ESP warning light functions.
[0045] Convergence is detected when the D9 value stabilizes or when the difference between two values from two successive processing loops is less than a predetermined threshold. The first loop 1 is executed, taking the compressor flow rate value as input, and then the second loop is executed.
[0046] Figure 3 illustrates the execution of three successive processing loops 1, 2, and 3 (referenced in circles) represented in the compressor field implemented by the engine control unit according to the maximum load estimation method of the invention. Processing loop 1 takes as input for module E1 the compressor setpoint flow rate value DBO, processing loop 2 takes as input for module E1 the flow rate value DB1 obtained at the output of module E5 during the execution of loop 1, and finally, processing loop 3 takes as input the flow rate value DB3 obtained at the output of module E5 during the execution of loop 2. The values of DB1 and DB2 are illustrated and obtained from the line C1 at constant engine speed and the equivalent maximum load at the maximum pumping limit ratio. Rp2 is the maximum potential ratio of the compressor field at the instantaneous operating points of the engine.
[0047] The invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention by combining, for example, the different features mentioned above, taken alone or in combination, without departing from the scope of the invention.
Claims
CLAIMS 1. Method for estimating the maximum potential load (D9) of a turbocharged internal combustion engine implementing a calculation chain comprising the following successive steps of determining (E1) the maximum compression ratio (D2) of a compressor as a function of a parameter representative of the flow rate of the compressor, determining (E2) a maximum pressure (D4) at the compressor outlet as a function of the maximum compression ratio (D2), determining (E3) a maximum pressure (D6) in the intake manifold as a function of the maximum pressure (D4) at the compressor outlet, determining (E4) the maximum load (D9) as a function of the maximum pressure (D6) in the intake manifold, characterized in that the calculation chain further comprises determining (E5) a maximum flow rate of the compressor (D10) corresponding to the maximum load (D9) and looping back the calculation chain (E1, E2, E3,E4) taking as input the maximum flow rate (D10) to determine a new value of the maximum load (D9) from at least a second processing loop of the calculation chain (E1, E2, E3, E4)., 2. Method according to claim 1 in which successive values of the maximum load (D9) are recalculated from processing loops of the calculation chain taking as input the last maximum flow rate value (D10) until the detection of a convergence between two maximum load values (D9) from two successive processing loops of the calculation chain (E1, E2, E3, E4).
3. Method according to claim 1 or 2, in which the determination (E1) of the maximum compression ratio (D2) is determined from a mapping of the maximum compression ratio of a field of the compressor taking as input values of the flow rate of the compressor (D1; D10).
4. Method according to any one of claims 1 to 3, in which the determination (E2) of the maximum pressure (D4) at the outlet of the compressor as a function of the maximum compression ratio (D2) is determined from an instantaneous estimate or measurement of the pressure (D3) at the inlet of the compressor.
5. Method according to any one of claims 1 to 4, in which the determination (E3) of the maximum pressure (D6) in the intake manifold is calculated from a pressure difference (D5) between the compressor and the intake lines of the engine, in which the pressure difference (D5) is obtained by a map taking as input a measurement or estimate of the instantaneous flow rate of the turbocharger.
6. Method according to any one of claims 1 to 5, in which the determination (E4) of the maximum load (D9) is calculated from a load equation according to the following relation: Cmax = A*P2”max + B, where Cmax is the maximum load, P2”max is the maximum pressure in the intake manifold, A a filling coefficient and B an offset coefficient, where the coefficients A and B are calculated as a function of mapping taking engine operating points as input.
7. Method according to any one of claims 1 to 6, in which the determination (E5) of the maximum flow rate (D10) is calculated according to the following relationship: DBmax=Cmax*K, where DBmax is the maximum flow rate, K is a coefficient delivered by a map taking the instantaneous engine speed as input and Cmax is the maximum load.
8. Control unit of a pressed internal combustion engine configured for implementing the method for estimating the maximum potential load of the engine according to any one of claims 1 to 7.
9. Computer program comprising instructions which, when the program is executed by a control unit of an internal combustion engine, cause the latter to implement the method for estimating the maximum potential load of the engine according to any one of claims 1 to 7.
10. Motor vehicle comprising a turbocharged internal combustion engine controlled by a control unit according to claim 8.