Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/30—Controlling fuel injection
  • F02D41/38—Controlling fuel injection of the high pressure type
  • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
  • F02D41/402—Multiple injections
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1401—Introducing closed-loop corrections characterised by the control or regulation method
  • F02D2041/1433—Introducing closed-loop corrections characterised by the control or regulation method using a model or simulation of the system
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/02—Input parameters for engine control the parameters being related to the engine
  • F02D2200/06—Fuel or fuel supply system parameters
  • F02D2200/0602—Fuel pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/02—Input parameters for engine control the parameters being related to the engine
  • F02D2200/06—Fuel or fuel supply system parameters
  • F02D2200/0602—Fuel pressure
  • F02D2200/0604—Estimation of fuel pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2250/00—Engine control related to specific problems or objectives
  • F02D2250/04—Fuel pressure pulsation in common rails
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/40—Engine management systems

Definitions

• the present invention concerns, on the one hand, a method for controlling an injection system of an internal combustion engine having a common rail, and on the other hand an injection system and an automotive vehicle.
• an engine electronic control unit EECU
• start time and duration on which depend the injected fuel quantity, of each fuel injection into one of the cylinders of the engine.
• the fuel quantities and the start times are computed based on the required engine torque and in accordance with requirements relative to the emissions of pollutant gases and temperature, depending on injection conditions such as fuel temperature, common rail pressure and injectors wear.
• a plurality of separate fuel injections may be fed into each cylinder during a given cylinder cycle, in order to reduce the combustion noise and noxious emissions.
• US-B-7 152 575 discloses a method for controlling the fuel injections in an internal combustion engine.
• a characteristic map is used to determine a mapping value for the injection durations, in dependence on the fuel pressure and the fuel quantity to be injected.
• This estimated mapping value does not take into account the pressure fluctuations in the common rail and is corrected with a formula which takes into account the pressure fluctuations caused by the preceding injections of the cylinder cycle.
• This method is long and complicated and consequently, it requires expensive hardware and the injected fuel quantities are not precise.
• the aim of this invention is to provide an improved method for controlling the fuel injections in an internal combustion engine of an automotive vehicle.
• the invention concerns a method for controlling an injection system in an internal combustion engine having a common rail, for injecting fuel to cylinders, each injection phase comprising several individual injections occurring during a cylinder cycle, the method including:
• the adaptive model is adjusted between cylinder cycles, depending on the difference between the computed and the recorded pressure values. In this way, the computed pressure values are more accurate, which allows improving the precision of the injected fuel quantities.
• such a method may incorporate one or several of the following features:
• the process comprises a fifth step, in which the first, second, third and fourth steps are repeated for the following injection phases.
• the adaptive model includes a first adaptive map giving a pressure drop inside the common rail caused by a preceding individual fuel injection.
• the pressure drop given by the first adaptive map depends on the injected fuel quantity during the preceding individual fuel injection and on the pressure inside the common rail before that injection.
• the adaptive model includes a second adaptive map giving the pressure variance inside the common rail between a first and a second injection, especially between two consecutive individual injections, more especially between a given individual injection and an immediately preceding individual injection.
• the pressure variance given by the second adaptive map depends on the pressure at the end of the first injection and on the start time of the second injection.
• the pressure in the common rail is measured before and after each individual injection.
• the adaptive model is specific to each cylinder.
• the adaptive model includes at least one three dimensional matrix.
• the method includes an initialization step occurring during a subsequent use of the engine, wherein the steps are repeated once with the values of the adaptive model established during the prior use of the engine.
• the invention also concerns an injection system for an internal combustion engine having a common rail for supplying fuel to cylinders and means for measuring the pressure in the common rail, and further including a control unit implementing such a method.
• the invention concerns an automotive vehicle, including such an injection system.
• FIG. 1 is a schematic representation of an injection system of an automotive vehicle according to the invention ;
• - figure 2 is a graph showing the position of a cylinder of the engine depending on the angular position of the crankshaft of the engine ;
• FIG. 3 is a graph showing the pressure variations in a common rail of the automotive vehicle depending on the time ;
• FIG. 4 is a bloc diagram of a method according to the invention.
• FIG. 1 Some parts of an automotive vehicle V, for example a truck, are schematically represented on figure 1 and are part of a fuel injection system S of an internal combustion engine E.
• the injection system S comprises a common rail R where high pressure fuel is accumulated.
• the fuel injection system S may include a low pressure fuel pump P1 which moves the fuel contained in a fuel tank T into an entry duct D1 connected to the input of a high pressure fuel pump P2 feeding the common rail R.
• a first valve V1 may be located on the entry duct, between pumps P1 and P2.
• a second valve V2 may be located on a return duct D2 which brings back the fuel contained in the common rail R into the fuel tank T.
• the common rail R feeds fuel to a number of injectors, for example six injectors 11 , 12, 13, 14, 15 and 16, each injecting fuel into a cylinder C1 , C2, C3, C4, C5 or C6 of the engine E.
• Each cylinder C1 to C6 includes a combustion chamber 4 closed by a piston 5 attached to a connecting rod 6 linked to a crankshaft 7.
• the injectors may inject the fuel directly in the corresponding combustion chamber.
• an engine electronic control unit 1 receives a signal S P carrying information relative to the pressure P in the common rail R, measured by a pressure sensor 2.
• the control unit 1 delivers signals S V i and S V2 for the opening and the closure of the valves V1 and V2, depending on the amount of fuel needed inside of the common rail R.
• the control unit 1 also delivers a signal S r to each injector 11 to 16 for driving the opening and the closure of the injectors 11 to 16.
• Figure 2 shows the position of the piston 5 of the first cylinder C1 during one cylinder cycle, depending on the angular position ⁇ of the crankshaft 7.
• a sensor 8 measures and transmits the angular position ⁇ to the control unit 1, via a signal S u .
• the other cylinders C2 to C6 follow the same cycle, with an angular offset which, in the case of a six cylinder engine, is typically of 120° between each of them so that the cycles of the cylinders C1 to C6 repeat in a loop.
• each injection phase includes a number of separate individual fuel injections, for example three separate individual fuel injections B, M and A shown on figure 3:
• main injection M which starts at a main-injection time t M , lasts for a main- injection duration d M and during which a fuel quantity Q M is injected into one of the cylinders C1 to C6,
• pre-injection B which starts before the main injection M at a pre-injection time t B , lasts for a pre-injection duration d s , and during which a fuel quantity Q B is injected into the same cylinder C1 to C6,
• a post-injection A which starts after the main injection M, at a post-injection time t A , lasts for a post-injection duration d A and during which a fuel quantity Q A is injected into the same cylinder C1 to C6,
• the injection phase is repeated for the cylinder cycles of the following cylinder.
• the fuel quantities Q B , QM and Q A injected into the chamber 5 are calculated by the control unit 1 depending on the required engine torque.
• the fuel quantities Q B , QM and Q A physically depend inter alia on the injection durations d B , divi and d A and on the pressure P inside the common rail R.
• the injection times t B , t M and t A and the injection durations d B , d M and d A are expressed in terms of angular positions ⁇ of the crankshaft 7.
• the angular top dead centre GO T DC of the crankshaft 7 corresponds to a top dead centre time tjoc equal to zero.
• the pressure P inside the common rail R decreases during each injection B, M and A because the fuel quantities Q B , Q M and Q A are removed from the common rail R.
• the pressure P inside the common rail R fluctuates between the injections B, M and A most notably due to acoustic effects caused by the closure of the injector 11 , 12, 13, 14, 15 or 16.
• the control unit 1 needs to know the value of the pressure P at the beginning of each individual injection B, M and A in order to compute the injection times t M , t A and t B and the injection durations d M , d B and d A of the next injection cycle.
• the control unit 1 cannot physically obtain the pressure P and re-calculate the opening times between each individual injections B, M and A because the duration between the individual injections B, M and A is too short relative to embedded control constraints. However, the control unit 1 knows the angular position ⁇ of the crankshaft 7, which correspond to the injection times t M , t A and t B .
• the control unit 1 has to compute the initial values P Bi , P Mi and P Ai of the pressure P, immediately prior to each injection B, M, A, and the final values P Bf , P Mf and P Af of the pressure P immediately after each individual injection B, M and A.
• the subscript "i” stands for "initial”, because the pressure P immediately prior to each injection B, M and A is considered equal to the pressure at the beginning of the injection B, M and A.
• the subscript "f stands for "final” because the pressure P immediately after each injection B, M and A is considered equal to the pressure at the end of the injection B, M and A.
• This prediction is made with an adaptive model of the pressure P in the common rail R.
• This adaptive model may include adaptive maps K and W.
• the adaptive map K gives first-order variations of the pressure.
• the adaptive map K is specific to each cylinder C1 to C6 but in a variant, there may be a single adaptive map K for all the cylinders C1 to C6.
• the adaptive map W gives second-order variations of the pressure and is optional.
• the adaptive model includes six maps K and six maps W.
• the pressures P BI , PMI, PAI. p Bf, Piw and P AF are then used by the control unit 1 in order to compute, for the next injection phase, each injection time t M , t B and t A and each injection duration d M , d B and d A , so that the required quantities of fuel Q B , QM and Q A are injected at the required injection times t M , t A and t B .
• the adaptive map K gives the pressure drop ⁇ ⁇ inside the common rail R caused by the injection B, M or A, depending on the quantity of fuel Q B , Q M or Q A injected and on the initial pressure P BI , P MI or P AI inside the common rail R, before the injection B, M or A.
• the pressure P BF at the end of the pre-injection B equals to the pressure P BI at the beginning of the pre-injection B, minus the pressure drop ⁇ ⁇ given by the adaptive map K, depending on the fuel quantity Q B of the pre-injection and on the pressure P BI at the beginning of the pre-injection B:
• n be a given individual injection, for example the injection B, M, or A.
• the pressure P nt at the end of a given injection n equals to the pressure P recreationali at the beginning of this injection n, minus the pressure drop ⁇ ⁇ given by the adaptive map K, depending on the fuel quantity Q n of this injection n and on the pressure P ⁇ at the beginning of this injection n :
• the adaptive map W gives the pressure variance AP W , at the injector's 11 to 16 connexion point with the common rail R, between a first and a second individual injections B, M or A, depending on the relative time offset between the first injection and the second individual injection, and depending on the pressure inside the common rail at the end of the first injection.
• the pressure variance may be expressed depending on the relative time between two consecutive individual injections, more especially between a given individual injection and an immediately preceding individual injection.
• the pressure P Mi at the beginning of the main injection M equals to the pressure P Bf at the end of the pre-injection B minus the pressure variance AP W given by the adaptive map W, depending on the relative timing RT B ⁇ M between the end of the pre- injection B and the main injection M start time t M , and depending on the pressure P Bf at the end of the pre-injection B:
• the pressure variance AP w may be positive or negative.
• adaptive maps K and W are two dimensional matrices, or look-up tables.
• the maps could have more dimensions if it were chosen to further refine the evaluation of the pressure drop and of the pressure variance.
• the pressure drop caused by a preceding individual injection or the pressure variance could take into account a variable affecting the fuel compressibility, the fuel viscosity, etc.. Therefore, the maps could have further dimensions for taking into account variables such as the fuel temperature, fuel composition (in particular fuel blends), etc...
• the method includes a preliminary step 1000, taking place prior to the use of the vehicle V, during which initial values are programmed in the adaptive maps K and W at stable conditions, at steady speed, by measuring the rail pressures P' Bi , P' Mi , P' Ai , P' Bf , P' Mf and P' Af , the injected fuel quantities Q B , Q and Q A and the injection times t M , t A and t B .
• specific adaptive maps K and W are used for each cylinder C1 to C6, the measures have to be repeated for each cylinder C1 to C6.
• the control unit 1 computes the required fuel quantity Q M to inject in this cylinder C1 to C6 during the main injection M, depending on the requested engine torque.
• the injection time t M of the main injection M, as well as the fuel quantities Q B and Q A and the injection times t A and t B of the injections A and B of this injection phase, are also set by the control unit 1 according inter alia to combustion efficiency, emission, noise and heat constraints.
• the adaptive maps K and W are used to compute estimated pressures P BI , P M ⁇ , PAI. ⁇ * > IW and P Af for the coming injection cycle. This step is therefore performed for a given injection phase and is completed before the beginning of said injection phase.
• the pressure P B , at the beginning of the pre-injection B is calculated, depending on a rail pressure P' measured by the sensor 2 about 60° before the angular top dead centre ⁇ ⁇ of the cylinder cycle, before the beginning of the injection phase.
• a rail pressure P' measured by the sensor 2 about 60° before the angular top dead centre ⁇ ⁇ of the cylinder cycle, before the beginning of the injection phase.
• the pressure P B is then considered to be equal to the measured pressure P'.
• the pressure P BI at the beginning of the pre-injection B may be calculated depending on the maximum pressure P' MAX inside the common rail R, measured by the sensor 2.
• the pressure P BI may be considered equal to the maximum pressure P' MAX .
• the pressure P BI may be calculated depending on the maximum pressure P' MAX and on the difference in time At between the time t Pmax when the pressure P is equal to the maximum pressure P MAX and the injection time t B of the pre- injection B of the upcoming injection phase.
• the pressure P Bf at the end of the pre-injection B is calculated with the adaptive map K.
• the pressure P BF equals to the pressure P BI minus the pressure drop ⁇ ⁇ given by the adaptive map K, depending on the fuel quantity Q B of the pre-injection and the pressure P BI at the beginning of the pre-injection B:
• the injection duration d B of the pre-injection B is calculated depending inter alia on the fuel quantity Q B of the pre-injection B and on the pressure ⁇ ⁇ , at the beginning of the pre-injection B.
• the relative timing RT B _,M between the end of the pre-injection B and the injection time t M of the main injection M is calculated depending on the injection duration d B of the pre-injection B, and on the injection times t B and t M of the pre-injection B and of the main injection M, calculated during step 2000:
• the pressure P Mi at the beginning of the main injection M is calculated with the adaptive map W.
• the pressure P Mi equals to the pressure P Bf minus the pressure variance AP W given by the adaptive map W, depending on the relative timing RT B ⁇ M between the end of the pre-injection B and the main injection M start time t M, and depending on the pressure P Bf at the end of the pre-injection B:
• the pressure P Mf . at the end of the main injection Ivl is calculated with the adaptive map K.
• the pressure P Mf equals to the pressure P i at the beginning of the main injection M minus the pressure drop ⁇ ⁇ given by the adaptive map K, depending on the fuel quantity Q M of the main injection M and on the pressure P Mi at the beginning of the main injection M:
• the value of the pressure P Mi at the beginning of the main injection M is given by sub-step 3004.
• the injection duration d M of the main injection M is calculated depending inter alia on the fuel quantity Q M of the main injection M and on the pressure P M at the beginning of the main injection M. Then, in the sixth sub-step 3006, the relative timing RT M ⁇ A between the end of the main injection M and the injection time t A of the post-injection A is calculated depending on the injection duration d M of the main injection M, and on the injection times t M and t A of the main injection M and of the post injection A, calculated during step 2000.
• the pressure P Ai at the beginning of the post-injection A is calculated with the adaptive map W.
• the pressure P Ai equals to the pressure P Mf at the end of the main injection M minus the pressure variance AP W given by the adaptive map W, depending on the relative timing RT M ⁇ A between the end of the main injection M and the post-injection A start time t A , and depending on the pressure P Mf at the end of the main injection M:
• PAI Piw- AP W - P M f - W(RTM ⁇ A, PIW)-
• the value of the pressure P f at the end of the main injection M is given by sub-step 3005.
• the pressure P A , at the end of the post-injection A is calculated with the adaptive map K.
• the pressure P Af equals to the pressure P Ai at the beginning of the post-injection A minus the pressure drop ⁇ ⁇ given by the adaptive map K, depending on the fuel quantity Q A of the post-injection M and the pressure P Ai at the beginning of the post-injection A:
• the injection duration d A of the post-injection A is calculated depending inter alia on the fuel quantity Q A of the post-injection A and on the pressure P Ai at the beginning of the post-injection A.
• this part of the process includes the sub-steps of, for a given individual injection:
• control unit 1 has predicted the values of all the pressures P B i, P I, PAI > P-t f . Piw and P Af for the coming injection cycle. This first prediction is not precise since it does not take into account the pressure fluctuations occurring in operation, because adaptive maps K and W are filled with initial valued.
• the injection system S performs the injections B, M and A.
• the control unit 1 sends the signal Si to the given injector amongst the injectors 11 to 16, and the sensor 2 records the measured rail pressures P' Bi, P'MII P'AI, P'efi P'wif and P' A f at the beginning and at the end of each injection B, M and A.
• the pumps P1 and/or P2 might be actuated by the control unit 1 in order to feed fuel into the common rail 1. In this case, the pressure P inside the common rail increases.
• the pumps P1 and P2 are not necessarily actuated between each injection phase.
• the pressure P B i at the beginning of the pre-injection of the next injection phase may be considered equal to the pressure P Af at the end of the post-injection A of the preceding injection phase plus the pressure variance AP W inside the common rail R after the post- injection A of the preceding injection phase.
• the pressure variance AP W may be neglected.
• a step 5000 the values programmed in the adaptive maps K and W, for example during step 1000, are replaced with new values based on the comparison between the calculated pressure values P B i, PMI. PAI, P_>f. Piw and P A f computed during step 2000 and the measured values P' Bi. P' MII P' A II P'EHI P Mt and P' A f recorded during step 4000.
• the new values are preferably incorporated gradually to the adaptive maps K and W.
• the new values may represent 10% of the preceding values of the adaptive maps K and W:
• the steps 2000 to 5000 may be repeated at the next injection phase for the given cylinder.
• the same process is also carried out in parallel for the other cylinders C1 to C6, with an angular offset of 120° between'each of them, with the adaptive maps K and W corresponding to the considered cylinder C1 to C6.
• step 2000 the adaptive maps K and W, programmed with modified values set during , step 5000 of the preceding cylinder cycle, are used to compute the fuel quantities Q B , Q M and Q A and the injection times t B , t M and t c of the next cylinder cycle of cylinder C1 , and so on for the other cylinders C2 to C6.
• the adaptive maps K and W are used to estimate precisely the pressure P in the common rail R for the next injection phase, by taking into account the rail pressure P fluctuations.
• the injected fuel quantities Q B , Q M and Q A are very close to the computed values.
• Arrow 7000 on figure 4 shows an initialization step occurring during a subsequent use of the vehicle V, when the engine E starts.
• the steps 2000 to 5000 are performed once with the values of the adaptive maps K and W established during the prior use of the vehicle. Then, the steps 2000 to 5000 are repeated in a loop as described previously.
• the values programmed in the adaptive maps K and W are replaced with new values only when the engine E is warm and runs in a steady state.
• the step 5000 of the method according to the invention is performed only when the engine E runs in a steady state.
• this step 5000 of updating the adaptive maps is not necessarily performed at each engine cycle. It can be performed from time to time, for example at regular intervals or it can be performed only during adapting periods which occur from time to time, preferably within steady state operating periods of the engine.
• the adaptive map W gives the pressure variance AP W inside the common rail R between a first and a second injection B, M or A, depending on the time offset between the injection start time of the second injection and the top dead centre
• RT B be the relative timing between the injection time t B of the pre-injection B and the top dead centre time t TDC .
• RT M be the relative timing between the injection time t M of the main injection M and the top dead centre time t T Dc
• RT A be the relative timing between the injection time t A of the post-injection A and the top dead centre time t TDC .
• the relative timings RT B , RT M and RT A are calculated in such a way that they have the same sign. In other words, the relative timings RT B , RT M and RT A are all positive or all negative.
• the method includes a step occurring after step 3000, in which the control unit 1 computes a delay ⁇ between the times when the fuel is injected and the moment when the signal Si is emitted, based on the measured rail pressure P' Bi at the beginning of the injection phase.
• the number of injectors 11 to 16 and cylinders C1 to C6 may vary. In this case, the angular offset between the positions of the cylinders is adapted.
• the engine E may equip another type of automotive vehicle, for example a car.
• the engine E may equip a machine different from a vehicle, or a fixed installation.
• the number of individual injections of each injection phase may vary. The technical features of the embodiments and variants mentioned here above can be combined.

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• 2012
  • 2012-12-14 EP EP12840856.4A patent/EP2932075A1/de active Pending
  • 2012-12-14 WO PCT/IB2012/003059 patent/WO2014091273A1/en active Application Filing

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