System and method for controlling an internal combustion engine for a motor vehicle in transit

0001The invention relates to the field of control of internal combustion engines with partial recirculation of exhaust gases with sequential control, and more particularly the control of such engines during a transient regime.

0002Internal combustion engines are controlled by control systems developed at the factory. The systems are developed by scanning several discrete values ​​of control quantities. The adjustments are thus carried out in a stabilized regime, that is to say in an operating phase in which the control parameters do not vary.

0003However, when the vehicle is moving, the internal combustion engine goes through a succession of stabilized operating phases separated by transient operating phases.

0004During the transient operating phases of an internal combustion engine, the internal combustion engine does not operate under conditions similar to those of the calibration. If the system does not have time to adapt to the new operating conditions, the various regulation methods are not effective. This is particularly the case when changing gear ratios or during decelerations followed by re-acceleration.

0005To be able to regulate the operation of the internal combustion engine during these phases, it is necessary to accelerate the response time of the system.

0006According to one embodiment of the invention, there is provided a system for controlling an internal combustion engine of the diesel type equipped with a partial recirculation circuit for exhaust gases, comprising a means for estimating parameter settings admitted air. The control system comprises a means of estimating the exhaust richness, a means of determining a setpoint of the intake richness as a function of setpoints of admitted air parameters, and a means of correcting the at least one of the setpoints for admitted air parameters as a function of the estimation of the exhaust richness and the setpoint of the intake richness.

0007The control system has the advantage of being easily integrated into the structure for regulating the air intake of a vehicle, of using the sensors generally present on a vehicle and of being able to adapt to all types of circuits. partial exhaust gas recirculation. The control system also has the advantage of regulating the transient operating phases of an internal combustion engine in order to accelerate the response time of the system, which has the effect of reducing emissions of polluting species.

0008The means for determining a setpoint for the intake richness can comprise a mapping of the volume yield and storage means containing the value of the richness at stoichiometry, the gas constant and the displacement of the internal combustion engine.

0009The control system may include a means for measuring the temperature of the intake manifold, a means for measuring the engine rotation speed, and a means for estimating the richness at the exhaust. The means for correcting at least one of the set parameters of admitted air parameters may be able to determine a set point corrected for at least one of the set parameters of admitted air parameters as a function of the richness estimate of exhaust, the setpoint of the intake manifold, the temperature of the intake manifold, the engine speed, and the exhaust manifold.

0010The means of estimating the richness at the exhaust can be a measurement sensor.

0011The corrected intake air flow setpoint can correspond to the intake air flow setpoint if the internal combustion engine has stabilized operation.

0012The partial exhaust gas recirculation circuit can be pitted:<ul id="ul0001" list-style="dash" compact="compact"><li>between the engine and the turbocharger, or</li><li>between on the one hand the turbocharger and the fresh air intake and on the other hand the turbocharger and the exhaust, or</li><li>a combination of these two circuits.</li></ul>

0013The means for estimating the setpoints of admitted air parameters can be a map.

0014The intake air parameters may include the intake air pressure and the intake air flow.

0015According to another embodiment, a method is provided for controlling an internal combustion engine fitted to a motor vehicle, provided with a partial exhaust gas recirculation circuit, the control method comprising an estimation of parameter settings. admitted air. The ordering process further comprises the following steps:<ul id="ul0002" list-style="none" compact="compact"><li>the exhaust richness is estimated,</li><li>an intake richness setpoint is determined as a function of the setpoints of admitted air parameters, and</li><li>at least one of the setpoints of admitted air parameters is corrected as a function of the estimation of the exhaust richness and of the setpoint of the intake richness.</li></ul>

0016One can correct at least one of the parameters of admitted air parameters as a function of the engine rotation speed, the intake temperature and the exhaust richness.

0017The correction of at least one of the admitted air parameter setpoints may leave said admitted air parameter setpoint unchanged when the internal combustion engine is in stabilized operation.

0018The intake air parameters may include the intake air pressure and the intake air flow.

0019Other objects, characteristics and advantages will appear on reading the following description given only as a non-limiting example and made with reference to the appended drawing in which the single figure illustrates the main elements of a control system according to the invention.

0020A diesel-type internal combustion engine is generally provided with a turbocharger, the compressor of which is located between the intake of fresh air and the intake manifold of the engine. The turbocharger turbine is located between the engine exhaust manifold and the exhaust line. In order to control the composition of the gases drawn into the cylinders, certain internal combustion engines are provided with a partial recirculation circuit for the exhaust gases. A partial exhaust gas recirculation circuit allows part of the exhaust gases to be reinjected into the cylinders in order to modify the stoichiometry of the admitted gas mixture. A partial exhaust gas recirculation circuit (acronym: EGR for “exhaust gas recirculation” in English) can be located in the low pressure part of the engine, that is to say upstream of the compressor, or in the high pressure part, downstream of the compressor.

0021A low pressure EGR circuit is inserted between the compressor of the turbocharger on the one hand and the fresh air intake and on the other hand the turbine of the turbocharger and the exhaust.

0022A high pressure EGR circuit is pitted between on the one hand the turbocharger compressor and the intake manifold and on the other hand the turbocharger turbine and the exhaust manifold.

0023Finally, some internal combustion engines are fitted with a low pressure EGR circuit and a high pressure EGR circuit.

0024In the single figure, one can see a control system according to the invention. The control system 1 is connected at the input to sensors 2. The control system 1 comprises an estimation means 3. The estimation means 3 receives as input a value of the atmospheric pressure via the connection 8, a value of the fuel flow rate through the connection 9, a value of the ambient temperature through the connection 10 and a value of the speed of rotation of the internal combustion engine through connection 11.

0025The estimation means 3 emits at the output a setpoint for the air flow admitted by the connection 16 and a setpoint for the intake pressure by the connection 15. The means for estimating 3 comprises a map 5 of the admitted airflow and a mapping 4 of the intake pressure.

0026The inlet pressure setpoint is used to regulate the speed of rotation of the compressor separating the low pressure part and the high pressure part of the engine.

0027A determination means 6 receives as input the setpoint for the air flow admitted by the connection 16 and the inlet pressure setpoint by the connection 15 and outputs a composition setpoint in the intake manifold by the connection 18 The composition instruction in the intake manifold is also called the intake composition.

0028The admission composition instruction F_1sp is determined by applying the following equation: <maths id="math0001" num="(Eq. 1)"><math display="block"><msub><mi mathvariant="normal">F</mi><mrow><mn mathvariant="normal">1</mn><mo>⁢</mo><mi>sp</mi></mrow></msub><mo>=</mo><mfrac><mrow><mfenced separators=""><mi>PCO</mi><mo>+</mo><mn mathvariant="normal">1</mn></mfenced><mo>⋅</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>f_sp</mi></msub><mo>⋅</mo><mfenced separators=""><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>in_sp</mi></msub><mo>-</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>air_sp</mi></msub></mfenced></mrow><mrow><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>in_sp</mi></msub><mo>⋅</mo><mfenced separators=""><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>f_sp</mi></msub><mo>+</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>air_sp</mi></msub></mfenced></mrow></mfrac></math><img file="EP2655838B1_D0001.tif" /></maths>with PCO = stoichiometric richness value, 14.5 for diesel<ul id="ul0003" list-style="none" compact="compact"><li>m_{f_sp} = fuel flow setpoint</li><li>m_{in_sp} = air flow inspired by the cylinders</li><li>m_{air_sp} = air flow setpoint</li></ul>

0029The equation of the admission composition F_1sp has the particularity of not involving the richness setpoint in the exhaust.

0030Remember that the air flow sucked by the cylinders m_{in_sp} is calculated using the classical filling equation. <maths id="math0002" num="(Eq. 2)"><math display="block"><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mrow><mi>in</mi><mo>,</mo><mi>sp</mi></mrow></msub><mo>=</mo><msub><mi mathvariant="normal">η</mi><mi>xol</mi></msub><mo>⋅</mo><mfrac><mi>Born</mi><mn mathvariant="normal">120</mn></mfrac><mo>⁢</mo><mi>Vd</mi><mo>⁢</mo><mfrac><msub><mi mathvariant="normal">P</mi><mrow><mn mathvariant="normal">1</mn><mi>_sp</mi></mrow></msub><mrow><mi mathvariant="normal">R</mi><mo>⋅</mo><msub><mi mathvariant="normal">T</mi><mn mathvariant="normal">11</mn></msub></mrow></mfrac></math><img file="EP2655838B1_D0002.tif" /></maths>with η_flight = volumetric efficiency<ul id="ul0004" list-style="none" compact="compact"><li>NOT_e = motor rotation speed</li><li>Vd = displacement</li><li>p_{1_sp} = the inlet pressure setpoint</li><li>R = the constant of ideal gases</li><li>T₁₁ = the temperature downstream of the RAS</li></ul>

0031In the case of an internal combustion engine fitted with a partial recirculation of exhaust gases at low pressure, it can be assumed that the intake temperature T₁ is equal to the temperature downstream of the RAS T₁₁.

0032The correction means 7 receives as input the intake composition setpoint via the connection 18, the inlet pressure setpoint by a bypass 17 of the connection 15. the speed of rotation of the engine by the bypass 12 of the connection 11 , the inlet temperature via connection 13 and the richness at the exhaust via connection 14. The correction means 7 emits at output a corrected setpoint of initial air flow through connection 20.

0033The correction means 7 makes it possible to determine setpoints making it possible to accelerate the response of the EGR circuit regulation by forcing the commands of the actuators during transient operation.

0034The state of the intake manifold is described by the following system of two first order differential equations. <maths id="math0003" num="(Eq. 3)"><math display="block"><mrow><mo>{</mo><mtable columnalign="left"><mtr><mtd><msub><mover><mi mathvariant="normal">p</mi><mo>˙</mo></mover><mrow><mn mathvariant="normal">1</mn><mi>_sp</mi></mrow></msub><mo>=</mo><mfrac><mrow><mi mathvariant="normal">R</mi><mo>⋅</mo><msub><mi mathvariant="normal">T</mi><mn mathvariant="normal">1</mn></msub></mrow><msub><mi mathvariant="normal">V</mi><mn mathvariant="normal">1</mn></msub></mfrac><mo>⋅</mo><mfenced separators=""><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>air_sp</mi></msub><mo>+</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>epr_sp</mi></msub><mo>-</mo><msub><mi mathvariant="normal">η</mi><mi>flight</mi></msub><mo>⋅</mo><mfrac><mi>Born</mi><mn mathvariant="normal">120</mn></mfrac><mo>⁢</mo><mi>Vd</mi><mo>⁢</mo><mfrac><msub><mi mathvariant="normal">p</mi><mrow><mn mathvariant="normal">1</mn><mi>_sp</mi></mrow></msub><mrow><mi mathvariant="normal">R</mi><mo>⋅</mo><msub><mi mathvariant="normal">T</mi><mn mathvariant="normal">11</mn></msub></mrow></mfrac></mfenced></mtd></mtr><mtr><mtd><msub><mover><mi mathvariant="normal">F</mi><mo>˙</mo></mover><mn mathvariant="normal">1</mn></msub><mo>=</mo><mfrac><mrow><mi mathvariant="normal">R</mi><mo>⋅</mo><msub><mi mathvariant="normal">T</mi><mn mathvariant="normal">1</mn></msub></mrow><mrow><msub><mi mathvariant="normal">p</mi><mi>l_sp</mi></msub><mo>⋅</mo><msub><mi mathvariant="normal">V</mi><mn mathvariant="normal">1</mn></msub></mrow></mfrac><mo>⋅</mo><mfenced separators=""><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>egr_sp</mi></msub><mo>⋅</mo><mfenced separators=""><msub><mi mathvariant="normal">F</mi><mn mathvariant="normal">2</mn></msub><mo>-</mo><msub><mi mathvariant="normal">F</mi><mn mathvariant="normal">1</mn></msub></mfenced><mo>-</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mi>air_sp</mi></msub><mo>⋅</mo><msub><mi mathvariant="normal">F</mi><mn mathvariant="normal">1</mn></msub></mfenced></mtd></mtr></mtable></mrow></math><img file="EP2655838B1_D0003.tif" /></maths>

0035When we develop and reverse this system of equations, we get a solution of the following form. <maths id="math0004" num="(Eq. 4)"><math display="block"><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mrow><mi>air</mi><mo>,</mo><mi>sp</mi><mo>,</mo><mi>corr</mi></mrow></msub><mo>=</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mrow><mi mathvariant="normal">T</mi><mo>⁢</mo><mn mathvariant="normal">1</mn></mrow></msub><mo>+</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mrow><mi mathvariant="normal">T</mi><mo>⁢</mo><mn mathvariant="normal">2</mn></mrow></msub><mo>+</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mrow><mi mathvariant="normal">T</mi><mo>⁢</mo><mn mathvariant="normal">3</mn></mrow></msub><mo>+</mo><msub><mover><mi mathvariant="normal">m</mi><mo>˙</mo></mover><mrow><mi mathvariant="normal">T</mi><mo>⁢</mo><mn mathvariant="normal">4</mn></mrow></msub></math><img file="EP2655838B1_D0004.tif" /></maths>with M_T1 = <i>f</i>(<i>T</i>₁, <i>F</i>₂, <i>F</i>_{1_<i>sp</i>}, <i>p</i>_{1_<i>sp</i>}) <ul id="ul0005" list-style="none" compact="compact"><li>m_T2 = <i>f</i>(<i>T</i>₁, <i>F</i>₂, <i>F</i>_{1_<i>sp</i>}, <i>p</i>_{1_<i>sp</i>})</li><li>m_T3 = <i>f</i>(<i>T</i>₁, <i>p</i>_{1_<i>sp</i>})</li><li>m_T4<i>f</i>(<i>T</i>₁, <i>F</i>₂, <i>F</i>_{1_<i>sp</i>}, <i>p</i>_{1_sp}<i>, Born</i>)</li></ul>and with F₂ = the richness measurement at the exhaust.

0036The first three terms contain the derivatives of the pressure or the composition setpoint in the intake manifold. In steady state, these terms are null. The stationary value of the corrected setpoint is then given by the fourth term.

0037The temperature in the intake manifold, the engine rotation speed and the richness are the main measures involved in determining the corrected setpoint. The wealth measure can be replaced by an estimate.

0038The control system 1 outputs the inlet pressure setpoint and a corrected intake air flow.

0039The control system thus makes it possible to correct the control setpoints of an internal combustion engine so as to override the control setpoints in stabilized operation and to improve the operation during transient operation. Emissions of polluting species and smoke are therefore reduced in stabilized operation and in transient operation.