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BR-102019023514-B1 - METHOD FOR DETERMINING THE MASS OF AIR TRAPPED IN EACH CYLINDER OF AN INTERNAL COMBUSTION ENGINE

BR102019023514B1BR 102019023514 B1BR102019023514 B1BR 102019023514B1BR-102019023514-B1

Abstract

METHOD FOR DETERMINING THE MASS OF AIR TRAPPED IN EACH CYLINDER OF AN INTERNAL COMBUSTION ENGINE Method for determining the mass (m) of air trapped in each cylinder (3) of an internal combustion engine (1), which comprises determining, based on a model that uses measured and/or estimated physical quantities, a value for a first group of reference quantities; determining, based on said model, the actual internal volume (V) of each cylinder (3) as a function of the rotational speed (n) of the internal combustion engine (1) and the closing delay angle (IVC) of the intake valve (5); and calculating the mass (m) of air trapped in each cylinder (3) as a function of the first group of reference quantities and the actual internal volume (V) of each cylinder (3).

Inventors

  • Marco Panciroli

Assignees

  • MAGNETI MARELLI S.P.A

Dates

Publication Date
20260317
Application Date
20191108
Priority Date
20181108

Claims (14)

  1. 1. Method for determining the mass of air (m) trapped in each cylinder (3) of an internal combustion engine (1); wherein the internal combustion engine (1) comprises a number of cylinders (3), each connected to an intake manifold (4), which receives fresh air through at least one respective intake valve (5) and to an exhaust manifold (6), into which the exhaust gases produced by combustion are introduced through at least one respective exhaust valve (7); and wherein the intake valves (5) and/or the exhaust valves (7) are controlled so as to alter their timing; the method comprising: - detecting the pressure P inside the intake manifold (4), the rotational speed n of the internal combustion engine (1) and a closing delay angle IVC of the intake valve (5); - determining a mass OFF of the gases produced by combustion in the previous work cycle and present inside the cylinder (3); - determining the internal volume V of each cylinder (3) as a function of the rotational speed n of the internal combustion engine (1) and the closing delay angle IVC of the intake valve (5); e- determine the mass of air trapped in each cylinder (3) by multiplying the pressure P by the internal volume V of each cylinder (3), from which the OFF mass of the gases is subtracted; the method being characterized by the fact that the step of determining the OFF mass of the gases comprises the sub-steps of: - calculating the MOVL mass of gases flowing, during an overlap phase in which each intake valve (5) and the respective exhaust valve (7) are simultaneously opened, from exhaust to intake and are drawn back into cylinder (3), during the subsequent intake phase, through the intake valve (5) by means of the following formula, in which the combustion chamber of cylinder (3) represents the passage section: SID - area of the ideal passage section; n - speed of the internal combustion engine (1); PO_REF - reference pressure upstream of the passage section; TO_REF - reference temperature upstream of the passage section; To - temperature upstream of the passage section; Po, P - pressure upstream and downstream, respectively, of the passage section; wherein the SID area of the ideal passage section is calculated by means of the product between a first function (A) of the speed n of the internal combustion engine (1) and the duration OVL of the overlap phase and a second function (G) of the speed n of the internal combustion engine (1) and the angular difference between the top dead center PMS (TDC) and the center of gravity G of the overlap phase; and - calculate the mass OFF of the gases as a function of the mass MOVL.
  2. 2. Method according to claim 1, characterized in that it comprises the additional steps of: - detecting the PEXH pressure of the exhaust gas flow and the TECH temperature of the exhaust gas flow; - calculating the mass of the off gases using the following equation: OFF = PEXH * Vcc / R * TEXH + MOV Vcc - dead volume of the combustion chamber of the cylinder (3); and R - constant of the fresh air and/or exhaust gas mixture.
  3. 3. Method, according to claim 1 or 2, characterized in that it comprises the additional step of calculating the OFF mass of the gases, in the case of P inside the intake manifold (4) being greater than the PEXH pressure of the gas flow in the exhaust, by means of the following equation: OFF = PEXH * Vcc / (R * TEXH) - MEXH_SCAV [16] Vcc - dead volume of the combustion chamber of the cylinder (3); MEXH.SCAV - residual mass of the exhaust gases present inside the combustion chamber of the cylinder (3) and directed directly to the exhaust manifold (6) through the respective exhaust valve (7); and R - constant of the fresh air and/or exhaust gas mixture.
  4. 4. Method according to claim 3, characterized in that the internal combustion engine (1) comprises a low-pressure exhaust gas recirculation circuit; the method comprises the additional steps of calculating a quantity (REGR) indicating the incidence of the low-pressure circuit on the gas mixture flowing in an intake duct (6); and calculating the OFF mass of the gases also as a function of said quantity, indicating the incidence of the low-pressure circuit.
  5. 5. Method, according to any of the preceding claims, characterized in that the internal volume V of each cylinder (3) is further calculated by means of a first map, which is a function of the closing delay angle (IVC) of the intake valve (5) and the rotational speed (n) of the internal combustion engine (1), as well as by means of a second map, which is a function of the pressure P inside the intake manifold (4) and the rotational speed of the internal combustion engine (1).
  6. 6. Method, according to any of the preceding claims, characterized in that the mass of air (m) trapped in each cylinder (3) is multiplied by a first factor, which is a function of the temperature (T) inside the intake manifold (4) and the pressure P and by a second factor, which is a function of the temperature (THZO) of the internal combustion engine coolant (1) and the pressure (P).
  7. 7. Method, according to any of the preceding claims, characterized in that the mass of air (m) trapped in each cylinder (3) is calculated as a function of a pair of multiplying coefficients (Ki, K2), which take into account the angular extension (WTi) of a difference from the reference values of the intake valve (5), the angular extension (WTE) of a difference from the reference values of the exhaust valve (7) and the speed (n) of rotation of the internal combustion engine (1).
  8. 8. Method, according to claim 7, characterized by the fact that the mass (m) of air trapped in each cylinder (3) is calculated as a function of a first multiplier coefficient (Ki), which takes into account the angular extension (WTi) of a difference relative to the reference values of the intake valve (5) and the angular extension (WTE) of a difference relative to the reference values of the exhaust valve (7) and a second multiplier coefficient (K2), which takes into account the speed (n) of rotation of the internal combustion engine (1) and the angular extension (WTE) of a difference relative to the reference values of the exhaust valve (7).
  9. 9. Method, according to any of the preceding claims, characterized in that the internal combustion engine (1) further comprises an exhaust gas recirculation (EGRLP, EGRHP) circuit, which in turn comprises a bypass duct (34, 26); along the bypass duct (34, 26) is disposed an EGR valve (35, 27), which is designed to adjust the flow of exhaust gases flowing through the bypass duct (34, 26); the method comprises determining the mass (m) of air trapped in each cylinder (3) as a function of a mass (MEGR) recirculated through the EGR circuit (EGRLP, EGRHP) for each cylinder (3).
  10. 10. Method, according to any of the preceding claims, characterized in that the dead volume Vcc of the combustion chamber of the cylinder (3) is a function of the speed (n) of rotation of the internal combustion engine (1) and of a first parameter (TVC), which is alternatively equal to the closing delay angle (EVC) of the exhaust valve (7) or to the greater value between zero and the lesser value between the closing delay angle (EVC) of the exhaust valve (7) and the value of the opening advance angle (IVO) of the intake valve (5) multiplied by -1.
  11. 11. Method, according to any of the preceding claims, characterized in that the volume (Vcc) of the combustion chamber of the cylinder (3) is determined by means of a third map, which is a function of the speed (n) of rotation of the internal combustion engine (1) and a first parameter (TVC), which is alternatively equal to the closing delay angle (EVC) of the exhaust valve (7) or to the greater value between zero and the lesser value between the closing delay angle (EVC) of the exhaust valve (7) and the value of the opening advance angle (IVO) of the intake valve (5) multiplied by -1 and by means of a fourth map, which is a function of the speed (n) of rotation of the internal combustion engine (1) and the duration of the overlap phase (OVL).
  12. 12. Method, according to any of the preceding claims, characterized in that it comprises the additional steps of: - determining, based on a calculation model using measured and/or estimated physical quantities, the mass (MOBJ) of combustion air required for each cylinder (3) in order to meet the torque requirement (Cr*); and - determining the value of the objective pressure (POBJ) within the intake manifold (4) based on said model as a function of the mass (MOBJ) of combustion air required for each cylinder (3) in order to meet the torque requirement (CT*), the actual internal volume (V) of each cylinder (3) and the first group of reference quantities.
  13. 13. Method, according to claim 12, characterized in that the internal combustion engine (1) comprises a valve (12), which is designed to adjust the flow of the gas mixture comprising exhaust gases and fresh air, i.e., air exiting from the outside, through the intake duct (8), directed to the intake manifold (4); the method comprises controlling said valve (12) so as to obtain the objective pressure (POBJ) value within the intake manifold.
  14. 14. Method, according to any of the preceding claims, characterized by comprising the additional step of calculating the mass (MSCAV) of fresh air within the intake manifold (4) directed directly to the exhaust manifold (6) by means of the difference between a mass (MOVL) flowing through the overlap, i.e., through the intake valve (5) and the exhaust valve (7) and the residual mass (MEXH.SCAV) of the exhaust gases present within the combustion chamber of the cylinder (3) and directed directly to the exhaust manifold (6) through the respective exhaust valve (7).

Description

Cross-referencing to related applications [001] This Patent Application claims priority from Italian Patent Application No. 102018000010164 filed on November 8, 2018, the full description of which is incorporated herein by reference. Technical field [002] The present invention relates to a method for determining the mass of air trapped in each cylinder of an internal combustion engine. known technique [003] As is known, a supercharged internal combustion engine, using a turbocharger system, comprises several injectors that inject fuel into their respective cylinders, each connected to an intake manifold by means of at least one respective intake valve and to an exhaust manifold by means of at least one respective exhaust valve. [004] The intake manifold receives a mixture of gases comprising exhaust gases and fresh air, that is, air exiting the external environment through an air intake duct, which is provided with an air filter for the fresh air flow and is regulated by a butterfly valve. Along the air intake duct, preferably downstream of the air filter, an air flow meter is also provided. [005] The airflow meter is a sensor connected to an electronic control unit and designed to detect the flow of fresh air drawn in by the internal combustion engine. The flow rate of fresh air drawn in by the internal combustion engine is an extremely important parameter for engine control, in particular, for determining the amount of fuel to be injected into the cylinders in order to obtain a given air/fuel ratio in an exhaust duct downstream of the exhaust manifold. However, the airflow meter is usually a very expensive and rather delicate component, as fuel vapors and dust can soil it, thus altering the reading of the value of the fresh air flow rate drawn in by the internal combustion engine. [006] State-of-the-art documents are published in US2017/248093, EP2594768 and US9109522. Description of the invention [007] The objective of the invention is to provide a method for determining the mass of air trapped in each cylinder of an internal combustion engine, the method being easy and economical to implement. [008] According to the invention, a method is provided for determining the mass of air retained in each cylinder of an internal combustion engine, as claimed in the appended claims. Brief description of the figures [009] The invention will now be described with reference to the accompanying drawings, showing a non-limiting configuration thereof, in which: - Figure 1 schematically shows a preferred configuration of an internal combustion engine provided with an electronic control unit implementing the method according to the invention; - Figure 2 shows, in detail, a cylinder of the engine of Figure 1; - Figures 3 and 4 schematically show the overlapping phase of an intake valve and an exhaust valve of the engine of Figure 1; and - Figure 5 shows the development of the β function used in the method according to the invention; Preferred invention settings [0010] In figures 1 and 2, the number 1 indicates, as a whole, an internal combustion engine, preferably supercharged by means of a turbocharger supercharging system. [0011] The internal combustion engine 1 comprises a number of injectors 2, which inject fuel directly into four cylinders 3 (preferably four cylinders arranged in line), each connected to an intake manifold 4 by means of at least one respective intake valve 5 (shown in figure 3) and to an exhaust manifold 6 by means of at least one respective exhaust valve 7 (shown in figure 2). For each cylinder 3 a corresponding injector 2 is provided; according to the configuration shown in figure 2, the injection is an indirect injection and therefore each injector 2 is disposed upstream of cylinder 3 in an intake duct 8 that connects the intake manifold 4 to cylinder 3. According to an alternative configuration not shown here, the injection is a direct injection and therefore each injector 2 is partially disposed within cylinder 3 through the end of the cylinder crown 3. [0012] According to figure 1, each cylinder 3 houses a corresponding piston 9, which is mechanically connected, by means of a connecting rod, to a drive shaft 10, in order to transmit to the drive shaft 10 itself, in a known manner, the force generated by the combustion inside cylinder 3. [0013] The intake manifold 4 receives a mixture of gases comprising exhaust gases (as described in detail below) and fresh air, i.e., air coming from outside through the intake duct 8, which is preferably provided with an air filter for the fresh air flow and is regulated by a butterfly valve 12, which is preferably an electronically controlled valve and which is movable between a closed position and a maximum open position. Furthermore, no air flow meter is provided along the intake duct 8. [0014] The intake valves 5 and/or the exhaust valves 7 are controlled with a VVT (variable valve timing) device, which acts hydraulically on the shaft that operates the intak