METHOD FOR ESTIMATING THE MAXIMUM POTENTIAL LOAD OF A SUPERCHARGED INTERNAL COMBUSTION ENGINE
The iterative calculation method for estimating the maximum load of a turbocharged engine addresses inaccuracies in existing methods, improving precision and reducing energy consumption by up to 65%, enhancing torque control and ESP system accuracy.
Patent Information
- Application Number
- FR2023000528
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-01-20
- Publication Date
- 2025-01-10
- Estimated Expiration
- 2043-01-20
AI Technical Summary
Existing methods for estimating the maximum potential load of a turbocharged internal combustion engine suffer from significant errors, particularly at low intake pressures, leading to inaccurate torque control and potential activation of the ESP system, resulting in unnecessary electrical energy consumption and incorrect warning light illumination.
A method involving a calculation chain with iterative loops to determine the maximum load, including determining the maximum compression ratio, outlet pressure, intake distributor pressure, and load, using existing engine sensors, and adjusting coefficients based on engine operating points to achieve convergence.
Improves the precision of maximum load estimation by up to 65%, enhancing torque control and reducing electrical energy consumption in hybrid vehicles, while ensuring accurate ESP system activation.
Smart Images
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Abstract
Description
Title of the invention: METHOD FOR ESTIMATING THE MAXIMUM POTENTIAL LOAD OF A SUPERCHARGED INTERNAL COMBUSTION ENGINE
[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 supercharging devices has become widespread in motor vehicles to minimize the emission of polluting gases. Among the software functions for controlling a supercharged engine, one of them is dedicated to continuously calculating the maximum potential load of the engine. The load is defined as the ratio between the mass of air admitted into the cylinders and the maximum admissible mass of air at the reference pressure of 1013 mbar. In the case of a turbocharged engine, the load is dependent on the action of the turbocharger.
[0003] For example, patent document US-B2-9080506 is known describing a method for controlling a supercharged engine equipped with a scroll valve that can be used to provide the necessary turbine power to cause increased recirculation of the compressor via a compressor recirculation valve. By coordinating the action of the compressor and the scroll valve, this solution allows the use of a larger compressor and turbine and consequently increases the compression ratio at low speed. It aims to improve the performance of the supercharging.
[0004] More precisely, a known calculation function of the maximum load involves a data processing chain taking into account, in particular, a characteristic map called compressor field delivering values of the compression ratio between the outlet pressure and the inlet pressure of the compressor, the characteristic maximum limit of which delimits the operating zone where the compressor does not act, called the pumping zone. The applicant has filed, for example, patent document FR-A1-2911371 describing a method for measuring the pumping limit of a compressor indicating these maximum compression ratio values. As taught in this document, this ratio is determined experimentally.
[0005] More precisely, the known models for estimating the maximum load of a turbocharged engine implement a calculation chain based on the characteristic curve of the compression ratio. From a compressor setpoint flow rate, a first processing is based on the compressor pumping limit to establish the maximum value of the compression ratio. Then, from this ratio and a measurement or estimation of the pressure at the compressor inlet, a second processing of the The calculation chain provides an estimate of the compressor outlet pressure. From this last value, a third processing, based on the airflow observed experimentally during operation in the supercharged zone of the engine between the compressor and the intake lines, allows the pressure in the intake manifold to be recalculated. Finally, a fourth processing based on a characteristic load equation of the engine allows the maximum load value to be established as a function of the pressure in the intake manifold.
[0006] In the operating zones furthest from the maximum potential, errors in the estimation of the maximum load were observed.
[0007] In [Fig.l], this situation is illustrated on a compressor field map representing on the ordinate the compression ratio P2 / P1 where P2 is the compressor outlet pressure and PI the inlet pressure, which can vary for example between a ratio of 1 to 3.5 depending on the compressor sizing. Compressor air flow Db values are shown. The compressor speed lines LVn are shown. Curve Cl is an iso-speed curve of the engine which indicates the compression ratio values as a function of the air flow. To the right of the slope break point is a compressor activation zone. The dotted line LP indicates the pumping limit equal to the maximum ratio values. The white zone above this limit is the pumping zone. Point Rpl is the maximum ratio for the compressor setpoint flow value DB0.According to the known estimation model, from this Rpl value a maximum load is estimated which is in fact the one corresponding to the set flow rate and not the maximum potential flow rate at iso-speed which would be the ratio Rp2. The maximum errors of this model can reach up to 65% in the areas furthest from the maximum potential of the engine, the areas with low intake pressure and mainly between 2000 and 3000 rpm in engine speed. Whereas on the other hand, the estimation of this model is rather correct in the high pressure areas where the engine potential is maximum.
[0008] This error can be detrimental when activating the ESP system (Electronic Stability Program). In particular, if the maximum potential load information is underestimated, in the case of a hybrid powertrain the torque structure strategies are likely to request electric motor torque to compensate for the lack of torque from the thermal engine without this being really necessary. This leads in particular to a consumption of electrical energy. Furthermore, the lighting of the ESP system indicator light depends on the difference between the load requested by the ESP and the estimate of the maximum engine load. If this estimate is too low the indicator light may not light up even though the ESP intervenes.
[0009] An objective of the invention is to overcome the aforementioned problems. The invention aims to improve the accuracy of the function for estimating the potential maximum load value of a supercharged internal combustion engine. Another objective is to provide an improved low-cost estimation solution. Another objective is to improve the control of the torque structure function by delivering a more accurate estimate of the maximum engine 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 flow rate,
[0012] - Determination of a maximum pressure at the compressor outlet as a function of the maximum compression ratio,
[0013] - Determining a maximum pressure in the intake manifold in function of the maximum pressure at the compressor outlet,
[0014] - Determination of the maximum load as a function of the maximum pressure in the intake manifold.
[0015] According to the invention, the calculation chain further comprises the determination of a maximum flow rate of the compressor 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 characteristics, alone or in combination:
[0017] - successive values of the maximum load are recalculated from loops processing of the calculation chain taking as input the last maximum flow rate value until the detection of convergence between two maximum load values from two successive processing loops of the calculation chain;
[0018] - the determination of the maximum compression ratio is determined from a car topography of the maximum compression ratio of a compressor field taking compressor flow values as input;
[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 compressor inlet pressure;
[0020] - the determination of the maximum pressure in the intake manifold is calculated from a pressure difference between the compressor and the engine intake lines, in which the pressure difference is obtained by a map 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 an equation of load 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 manifold, A a filling coefficient and B an offset coefficient, where coefficients A and B are calculated based on mapping taking engine operating points as input;
[0022] - the determination of the maximum flow rate is calculated according to the following relation: 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;
[0023] According to the invention, a control unit for a turbocharged internal combustion engine is envisaged, configured for implementing any one of the embodiments of the method for estimating the maximum potential load of the engine according to the invention.
[0024] Further contemplated is 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] A motor vehicle comprising a turbocharged internal combustion engine controlled by such a control unit is further envisaged.
[0026] The invention has the advantage of being an economical solution for improving the accuracy of the maximum potential load of the engine because it is based on a software calculation chain processing based on the existing sensors of the engine. The invention improves the torque structure function, in particular in the event of activation of an ESP system.
[0027] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, comprising embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which:
[0028] [Fig. 1] represents a graph of a compressor field making it possible to determine a maximum compression ratio of the compressor as a function of a set flow rate value of the compressor.
[0029] [Fig.2] schematically represents a block diagram of the calculation chain implemented 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 at iso-engine speed allowing the determination of a potential maximum compression ratio of the compressor.
[0031] The invention applies to vehicles comprising a powertrain equipped with a supercharged multi-cylinder internal combustion engine. It relates to vehicles with thermal or hybrid engines. The turbocharger may be of fixed geometry, of variable geometry with multi-blades or a sliding slide turbocharger. A turbocharger has the function of compressing the intake air necessary for the combustion of the fuel in order to increase the quantity of air admitted into the cylinders and thus increase the torque and power of the engine. The mechanical elements of the turbocharger are formed mainly by a turbine, a compressor and a shaft resting on a main bearing.
[0032] The engine control function comprises means for acquiring, measuring and estimating engine and turbocharger parameters enabling the implementation of the method for estimating the maximum load according to the invention, including the compressor setpoint flow rate, the engine speed, the temperature upstream of the compressor, the compressor field or even the engine flow rate as a function of the engine load. The maximum load parameter is used in particular for controlling the torque structure of a powertrain on which the various torque suppliers and the human-machine interface elements, such as the ESP activation lights, depend.It is recalled that the maximum engine load is defined as the ratio between the maximum air mass that can be admitted into the cylinders with regard to the operating limitations of the turbocharger and the engine and their specific characteristics known on the bench and the maximum air mass admissible at the reference pressure 1013 mbar. The invention aims to improve the accuracy of the estimation of the maximum load.
[0033] The control unit of an internal combustion engine is provided with an integrated circuit computer and electronic memories, the computer and the memories being configured to execute the method of estimating the maximum load. But this is not obligatory. Indeed, the computer could be external to the control unit, while being coupled to the latter. In the latter case, it can itself be arranged in the form of a dedicated computer comprising a possible dedicated program, for example. Consequently, the control unit, according to the invention, can be produced in the form of software modules (or computer software), or electronic circuits (or hardware), or a combination of electronic circuits and software modules.
[0034] In [Fig.2] we have represented the implementation of the estimation method by a chain calculation functions E1, E2, E3, E4 and E5 performing a data processing loop. The estimation function is triggered when the engine control unit is initialized and repeats the calculations continuously, every 10 milliseconds for example, during its operation.
[0035] The method comprises a first module E1 determining the maximum compression ratio D2 of a compressor as a function of a parameter DI representative of the flow rate of the compressor according to the estimation method. This parameter DI is a set flow rate value of the turbocharger compressor. The parameter DI is calculated continuously by the control of the turbocharger. The module E1 determines from the compressor field, recorded in the form of a map in the memory of the engine control unit, a maximum value D2 of the compression ratio corresponding to the pumping limit. The flow rate of the compressor is a reduced flow rate which can be defined by a coefficient of proportionality relative to the actual flow rate of the engine and for example according to the following relationship:
[0036] [Mathl]: Ïæ37] Qred = Q^
[0038] Where, Qred is the flow rate of the so-called reduced compressor, Q is the actual flow rate of the engine, Tl is the temperature upstream of the compressor, and PI is the pressure upstream of the compressor.
[0039] Then, the calculation chain includes the second calculation module E2 which makes it possible to estimate, according to the estimation method, as a function of the maximum value of the ratio D2 and the value D3 of the measured or estimated pressure PI at the inlet of the compressor, the value D4 of the maximum pressure at the outlet of the compressor.
[0040] The calculation chain further comprises a third calculation module E3 which makes it possible to estimate, according to the estimation method, as a function of the value D4 of maximum pressure at the outlet of the compressor and a negative pressure difference D5, induced by the flow of the air flow between the compressor and the intake distributor, a value D6 of maximum pressure in the intake distributor. The value D5 was determined experimentally on a test bench and can be determined at any time from a map or model assuming that the engine operates in the supercharged zone with the throttle open.
[0041] Then, the calculation chain comprises a fourth module E4 of the maximum load D9 as a function of the value D6 of maximum pressure in the intake manifold. More precisely, according to the estimation method the maximum load is calculated from a load equation according to the following relation: Cmax = A*P2' 'max + B, where Cmax is the value D9 of maximum load, P2' 'max is an estimate of the pressure in the intake manifold, A a filling coefficient corresponding to the value D7 in [Fig. 2] and B an offset coefficient corresponding to the value D8 in the same figure, where the values D7 and D8 are calculated as a function of functions, maps or models, known experimentally taking as input engine operating points, in particular the speed and the camshaft phase shifter 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 engine load D9 is calculated by executing the first processing loop for the compressor setpoint flow rate value, which may, in certain engine operating zones, differ significantly from the maximum engine flow rate value. This situation may result in an error of the order of 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 by means of a fifth calculation module E5 a value D10 of the maximum flow rate of the compressor 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 delivered by a map taking as input the instantaneous engine speed and Cmax is the last maximum load value calculated by the module E4. The map is recorded in the memory of the control unit and obtained experimentally in the design of the engine.
[0044] Processing loops of the calculation chain of modules E1, E2, E3, E4 and E5 are reiterated by taking as input of function E1 the value D10 calculated by the previous loop. The processing loops are reiterated until the maximum load value D9 converges towards a value of the maximum potential load. It has been observed that three or four iterative loops, i.e. 30 milliseconds or 40 milliseconds, are sufficient to obtain the maximum potential load value corresponding to the maximum potential flow rate of the engine at iso-speed. The accuracy of the maximum load estimation function is improved, which consequently improves the engine control functions dependent on the maximum potential load value, in particular the torque structure function, the intervention decisions of an electric motor machine in the case of a hybrid vehicle and in addition the ESP warning light lighting functions.
[0045] Convergence is detected when the value D9 stabilizes or when the difference between two values of two successive processing loops is less than a predetermined threshold. The first loop 1 is executed by taking as input the value of the compressor flow rate, then the second loop is executed.
[0046] In [Fig.3], the execution of three successive processing loops 1, 2, 3 (referenced in a circle) represented in the compressor field implemented by the engine control unit in accordance with the maximum load estimation method according to the invention is illustrated. Processing loop 1 takes as input for the module El the setpoint flow value of the compressor DBO, processing loop 2 takes as input for module El the flow 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 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 Cl at iso-engine speed and the maximum load equivalent to the maximum ratio of the pumping limit. Rp2 is the maximum potential ratio of the compressor field at the instantaneous operating points of the engine.
[0047] The invention is described in the above by way of example. It is understood that the person skilled in the art is able to produce different variant embodiments of the invention by associating, for example, the different characteristics 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 (El) 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 outlet of the compressor 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 outlet of the compressor, 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 (El, E2, E3,E4) by 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 (El, 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 (El, E2, E3, E4).
3. Method according to claim 1 or 2, in which the determination (El) of the maximum compression ratio (D2) is determined from a mapping of the maximum compression ratio of a compressor field taking as input compressor flow values (DI; 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 engine intake lines, 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 as input the instantaneous engine speed and Cmax is the maximum load.
8. A control unit of a turbocharged internal combustion engine configured to implement the method of estimating the potential maximum load of the engine according to any one of claims 1 to 7.
9. 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 the method for estimating the maximum potential load of the engine according to any one of claims 1 to 7.
10. A motor vehicle comprising a turbocharged internal combustion engine controlled by a control unit according to claim 8.