WO2017103803A1 - Appareil et procédé pour réguler la quantité de carburant injecté dans un moteur à combustion interne - Google Patents

Appareil et procédé pour réguler la quantité de carburant injecté dans un moteur à combustion interne Download PDF

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Publication number
WO2017103803A1
WO2017103803A1 PCT/IB2016/057601 IB2016057601W WO2017103803A1 WO 2017103803 A1 WO2017103803 A1 WO 2017103803A1 IB 2016057601 W IB2016057601 W IB 2016057601W WO 2017103803 A1 WO2017103803 A1 WO 2017103803A1
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WIPO (PCT)
Prior art keywords
fuel
injected
information
basis
pressure
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PCT/IB2016/057601
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English (en)
Inventor
Alessandro Ferrari
Original Assignee
Politecnico Di Torino
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Priority to EP16831733.7A priority Critical patent/EP3390798A1/fr
Publication of WO2017103803A1 publication Critical patent/WO2017103803A1/fr

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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
    • F02D41/3809—Common rail control systems
    • F02D41/3836—Controlling the fuel pressure
    • 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
    • F02D2041/1409—Introducing closed-loop corrections characterised by the control or regulation method using at least a proportional, integral or derivative controller
    • 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
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/26—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using computer, e.g. microprocessor
    • F02D41/28—Interface circuits
    • F02D2041/286—Interface circuits comprising means for signal processing
    • F02D2041/288—Interface circuits comprising means for signal processing for performing a transformation into the frequency domain, e.g. Fourier transformation
    • 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
    • F02D2200/0614—Actual fuel mass or fuel injection amount
    • 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
    • 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
    • F02D41/3809—Common rail control systems
    • F02D41/3836—Controlling the fuel pressure
    • F02D41/3845—Controlling the fuel pressure by controlling the flow into the common rail, e.g. the amount of fuel pumped
    • 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
    • F02D41/3809—Common rail control systems
    • F02D41/3836—Controlling the fuel pressure
    • F02D41/3863—Controlling the fuel pressure by controlling the flow out of the common rail, e.g. using pressure relief valves

Definitions

  • the present invention refers to an apparatus and to a method for controlling the quantity of fuel injected in an internal combustion engine; in particular, a Diesel cycle engine.
  • This problem can be faced in a satisfactory manner by controlling, among other things and with a high level of precision, the quantity of fuel introduced into the cylinders of an engine. In this manner, it is possible to reduce the quantity of unburned hydrocarbons produced by an internal combustion engine, since it is always injected a quantity of fuel that the engine can (almost) completely burn.
  • the injection systems according to the state of the art are capable of carrying out more than one injection in the course of every single operation cycle, so as to improve the polluting emissions, the efficiency and reduce the noise of the engine during its operation. Since the multiple injections per operation cycle have a lower duration with respect to a single injection, the capacity to estimate the quantity of fuel injected in the course of every single injection becomes, in current injection systems, even more important .
  • the present invention solves these and other problems by providing an apparatus (also referred as engine control unit) and a method for controlling the quantity of fuel injected in an internal combustion engine as in the enclosed claims.
  • the idea underlying the present invention is to (directly or indirectly) control the pressure of the fluid in the high- pressure fuel circuit, such that said pressure follows a pre- established trend, wherein said trend is determined on the basis of the quantity of fuel that it is necessary to inject into an internal combustion engine.
  • - fig. 1 illustrates a Common Rail injection system comprising an apparatus according to the invention
  • - fig. 2 illustrates the architecture of the engine control unit according to the invention included in the system of fig. 1 ;
  • - fig. 3 illustrates a mathematical model of part of the injection system of fig. 1;
  • - fig. 4 illustrates a block diagram of a system for controlling the quantity of injected fuel, comprising a first embodiment of the unit of fig. 2 which uses the model of fig. 3 ;
  • - fig. 5 illustrates a first variant of the injection system of fig. 1 comprising a second embodiment of the unit of fig. 2 which uses a mathematical model different from that of fig. 3 ;
  • - fig. 6 illustrates a variant of the mathematical model of fig. 3;
  • - fig. 7 illustrates a block diagram of a control system comprising the second embodiment of the apparatus according to the invention which uses the model of fig. 6;
  • FIG. 8 illustrates a block diagram of a control system comprising a third embodiment of an apparatus according to the invention.
  • FIG. 9 illustrates a block diagram of a control system comprising a fourth embodiment of an apparatus according to the invention.
  • an injection system 1 comprises the following parts:
  • a low-pressure fuel pump 2 positioned inside a tank 5 and adapted to generate a pressure capable of transferring the fuel (diesel, gasoline or other) , which is situated inside the tank, towards a high-pressure pump 11;
  • a fuel filter 3 which is in fluidic communication with the delivery side of said pump 2 and is adapted to remove the solid impurities that are found suspended in the fuel and/or to precipitate, on the bottom thereof, the water that is situated in solution in said fuel;
  • an injection pump 11 positioned downstream of the filter 11 and adapted to increase the value of the fuel pressure, preferably to several hundred bar, if the fuel is a gasoline, and to a value even greater than 2000 bar if the fuel is a diesel fuel;
  • a fuel rail 13 (also termed common rail or more simply rail), which is in fluidic communication with the delivery side of the injection pump 11 by means of a feed duct 131, wherein these ducts 13, 131 have mechanical characteristics (such as the material with which they are made, the shape, or other characteristics) such to allow the passage of a flow of fuel that is situated at the pressure generated by the injection pump 11;
  • a pressure sensor 12 which is at least partly positioned in the rail 13 and is configured for detecting the pressure of the fuel that flows at its interior;
  • valve FMV fuel metering valve 17 for controlling the flow rate at the pump inlet and preferably capable of damping the pressure oscillations due to the variation of the flow rate of the fuel flow;
  • At least one electro-injector 14 (which will be referred to in the course of this description with the term 'injector') ⁇ which is in flow communication with the fuel rail 13 via an injection duct 141 which has mechanical characteristics similar to the ducts 13,131, and wherein said injector 14 is configured for injecting upon command, i.e.
  • - engine control unit 16 (ECU, also referred as apparatus for controlling the quantity of injected fuel) adapted to supervise the operation of the engine, wherein said unit 16 is in signal communication, preferably by means of a network of CAN-BUS type or of another type, with at least the injection pump 11, the pressure sensor 12 and the injector 14, in a manner so as to be able to detect a fuel rail pressure p ra ii r ex P (i.e.
  • an injector activation signal act ⁇ n j and, optionally, a control signal dutycycle F1 4v for the valve FMV 17 which ensure that a predefined quantity of fuel is injected into the internal combustion engine.
  • both the injection pump 11 and the injector 14 are in fluid communication with the fuel rail 13 (high pressure) as well as with the fuel recovery duct 51 (low pressure) .
  • the pressures within the fuel rail 13 have an order of magnitude of thousands of bars, and therefore they can cause fuel leakage.
  • the Common Rail injectors for Diesel cycle engines comprise a pilot solenoid valve driven by a solenoid or by a piezoelectric element, wherein said valve is configured in a manner such that, when the injector actuation system is activated, the pilot valve is opened and allows the transit of a certain quantity of fuel coming from the rail 13 (high pressure) which causes the opening of the injector and, therefore, the injection of the fuel into the Diesel cycle engine.
  • This mechanism (necessary for operating at such high pressure values) produces, for each injection, a flow of fuel that is unloaded at low pressure from the pilot valve and which must be recovered by means of the fuel recovery duct 51.
  • this invention can be applied to Diesel cycle engines as well as to all other engine types (such as the Otto cycle engines, Atkinson cycle engines or engines of another type) that provide for the use of fuel injectors which also may not include the pilot valve.
  • the engine control unit 16 (also referred as apparatus for controlling the quantity of fuel injected into an internal combustion engine) will now be described; such unit 16 comprises the following components:
  • processing and control means 161 also termed computing means, such as one or more CPU, which govern the operation of the injection system 1, preferably in a programmable manner, by means of the execution of suitable instructions;
  • - memory means 162 such as a random access memory RAM and/or a Flash memory and/or memory of another type, which are in signal communication with the processing and control means
  • volatile memory means 162 are at least the instructions which can be read by the processing and control means 161 when the unit 16 is in an operating condition;
  • - acquisition means 163, such as an interface for a network of CAN-BUS type or of another type, which are in signal communication with the processing and control means 161 and are configured for detecting at least the pressure p ra ii r ex P of the fuel rail 13 and preferably the number of revolutions n pump of the pump 11 or even for detecting the current signal actually given to the injector;
  • - actuation means 164 such as an injector drive circuit, which are in signal communication with the processing and control means 161 and are configured for generating an electric current such to be able to energize the solenoid or the piezoelectric element of the injector 14 or to drive the operation of an injector drive circuit outside said unit 16 and/or such to drive the valve FMV 17;
  • I/O input/output means
  • I/O 165 which can for example be used for connecting said device 16 to peripheral devices or a programming terminal configured for writing instructions (which the processing and control means 161 will have to execute) in the memory means 162 and/or allowing the diagnostics of the injection system 1 and/or of the engine and/or of the entire vehicle on which said apparatus 16 is mounted;
  • input/output means 16 can for example comprise a CAN-BUS, USB, Firewire, RS232, IEEE 1284 or other adapter;
  • a communication bus 167 which allows the exchange of information between the processing and control means 161, the memory means 162, the acquisition means 163, the actuation means 164 and the input/output means 165.
  • the injection pump 11 can comprise means for measuring the rotation speed (such as an encoder, a tone wheel or other means) which allow measuring the rotation speed n pump of the pump 11.
  • the rotation speed n pump can also be determined, if the pump 11 is driven by means of a service belt driven by the engine axle, by detecting the number of revolutions of the engine and multiplying it by a mechanical transmission ratio; meanwhile, if the pump 11 is driven by an electric engine - preferably of synchronous type with permanent magnets, whose speed is controlled by the engine control unit 16, preferably by means of an Electronic Speed Controller (ESC) - the rotation speed n pump of the pump 11 might not be detected physically (i.e. it is not detected by using speed measurement means) but only by means of reading speed information from the memory means 162 (see Fig.
  • ESC Electronic Speed Controller
  • engine control information is stored which allows the unit 16 to control the operation of the engine in the different work conditions, associating injection information with each work condition. More in detail, this information is preferably stored in the form of maps which allow associating one or more inputs (such as the rotation speed of the engine, the temperature of the air, the temperature of the cooling water, the position of the gas pedal, the setting selected by the vehicle driver, the position of the butterfly valve if present or other inputs) with the respective injection information (quantity to be injected, nominal rail pressure, number of injections, etc.) .
  • the injection information defines the quantity of fuel that must be overall injected in the course of at least one part of an engine cycle; such quantity of fuel to be injected can be represented by means of a numeric value (integer or with floating point) corresponding to the quantity of fuel that must be injected in the course of a part of the engine cycle and, optionally, by a second numeric value which represents the number of injections that must be completed in the course of said part of the operation cycle.
  • the unit 16 is capable of computing the trend (i.e. at least one value) of the flow rate of fuel that must traverse the injector 14 in the time interval of said part of the engine cycle.
  • control unit 16 can be configured to determine the trend of said fuel flow rate in a manner such that in the course of the first and/or third injection, a fuel quantity is injected equal to a tenth of the quantity of fuel injected in the course of the second injection.
  • the quantity of fuel to be injected into the engine in the course of at least one part of an engine cycle can also be represented by means of a sequence of fuel flow rate values, wherein said sequence allows defining the trend of the flow rate of fuel that must traverse injector 14 in the course of said part of the engine cycle.
  • the trend of the flow rate of the fuel it is possible to define the trend of the flow rate of the fuel, so as to make possible the specification of a number of injections per (part of) arbitrary cycle, wherein in the course of each of said injections the injector 14 injects a pre-established quantity of fuel into the engine.
  • the injection information defines the quantity of fuel that must be injected in the course of at least part of an engine cycle and not of a complete engine cycle. This signifies that the unit 16 can be configured for varying the trend of the flow rate of the fuel flow to be injected in the course of a same engine cycle.
  • the unit 16 can monitor preferably by means of combustion sensors (which can for example comprise the piezoelectric elements of the injectors or dedicated piezoelectric sensors flush-mounted on the combustion chamber or other sensors) in signal communication with said unit 16 - that the injected fuel is actually burned/ignited and, in the case of poor combustion of the fuel injected in the course of at least one part of the engine cycle, vary the trend of the flow rate of the fuel flow preferably before the conclusion of said operation cycle, though also starting from the next operation cycle, so as to reduce the unburned fuel emissions and extend the operating lifetime of the lubricant.
  • combustion sensors which can for example comprise the piezoelectric elements of the injectors or dedicated piezoelectric sensors flush-mounted on the combustion chamber or other sensors
  • the acquisition means 163 are also configured for acquiring ignition information detected by the combustion sensors which are configured for detecting the pressure variations in the combustion chamber, and wherein the processing and control means 161 are configured for determining the flow rate of fuel to be injected q in j also on the basis of said ignition information which describes the evolution of the combustion in the cylinder.
  • a mathematical model M which is used by the engine control unit 16 for determining the trend of the pressure p r aii over time in the fuel rail 13 (wherein p rail is diffentiated from p ra ii r ex P due to the fact that it is determined by means of the model M, while Praii, exp ⁇ s detected by means of the pressure sensor 12) on the basis of the instantaneous flow rate q pU m P for the injection pump 11 and of the reference curve of the flow rate of the injected fuel q ⁇ n j which is preferably determined on the basis of the excitation time (ET) of the injector 14 actuation circuit and of the value of nominal rail pressure p n0 m (wherein ET and p n0 m are stored in the maps of the engine control unit); in addition, since the model M is preferably used for Diesel cycle engines, the model M described hereinbelow determines the trend of the pressure p ra ii over time
  • the engine control unit 16 determines the trend over time of the pressure p ra n by means of the model M on the basis of the instantaneous flow rates qi njf q P ump and preferably also of the flow rate q pv .
  • the model M is preferably a linear time-invariant model (LTI) with concentrated parameters, where part of the injection system 1 was modeled, from the hydraulic standpoint, as a zero-dimensional chamber network in which the pressure is uniform and can vary only with respect to time. These chambers are connected by means of single-dimensional ducts (these elements have a hydraulic capacity equal to zero in the model) and calibrated orifices.
  • LTI linear time-invariant model
  • the injection pump 11 was modeled as an entity having only a hydraulic capacity C lf wherein a fuel flow enters into said pump 11 through the port i having a flow rate q pU m P , and wherein said flow is introduced into the feed duct 131;
  • the feed duct 131 is modeled as an entity positioned downstream of the injection pump 11 and having a hydraulic resistance R 2 and a hydraulic inductance L 2 in series with each other, wherein a fuel flow transits in said rail 131 having a flow rate q 2 ;
  • the fuel rail 13 is modeled as an entity positioned downstream of the feed duct 131 and only having a hydraulic capacity C 3 ;
  • the injection duct 141 is modeled as an entity positioned downstream of the fuel rail 13 and having a hydraulic resistance R 4 and a hydraulic inductance L 4 ;
  • the injector 14 is modeled as an entity positioned downstream of the injection duct 141 and having four zero- dimensional chambers connected by three single-dimensional tubes .
  • a pilot valve control chamber modeled with a hydraulic capacity C 7 , wherein a fuel flow enters into said control chamber having a fuel flow rate q 6 and a fuel flow exits through a port P2 having a flow rate q pv , wherein said flow with flow rate q 6 enters into said control chamber by means of a duct which departs from the injector inlet and which is modeled with a hydraulic resistance R 6 and a hydraulic inductance L 6 in series with each other;
  • a pulverizer modeled with a hydraulic capacity C ll r wherein a fuel flow enters into said pulverizer, by means of the above-described duct, having a fuel flow rate q 10 , and a fuel flow exits through a port P3 having a flow rate q ⁇ n j.
  • the hydraulic inductance L 6 , the hydraulic resistance R 6 and the hydraulic capacity C 7 also might not be present if the injector 14 does not comprise the pilot valve (e.g. if the injector 14 is used in an Otto cycle engine or if the diesel injector is of piezoelectric type with direct actuation) .
  • j and q ne t,j are respectively the pressure and the rate in net mass that enters into the j-th chamber and the derivative of the pressure with respect to time.
  • the hydraulic capacity C j can be computed by means of the formula reported below:
  • V j and a-,- are respectively the volume of the j-th chamber and the speed of the local sound in the j-th chamber.
  • q j is the mass flow rate that flows into the j-th tube
  • Ap j is the pressure drop along the j-th tube.
  • the hydraulic inductance L j can be computed by means of the formula reported below:
  • the hydraulic resistance R j is computed in the case that the fuel flow flows into the tubes with a laminar motion. In this manner, it is possible to preserve the linearity of the equations and, therefore, prevent the structure of the control system implemented by the control unit 16 (described hereinbelow) from being excessively complicated; still in this case, the distributed load losses due to friction depend on the average properties (over time) of the fuel and on the geometric characteristics of the j-th tube. Therefore, the processing and control means 161 compute at least one trend over time of a reference pressure p ra ii by executing a sequence of instructions (which implements the model M) in which the motion of the fuel is considered along at least the injection duct 141 as a laminar motion. In a more complex variant of the algorithm, a modeling of the friction can also be considered that also accounts for the type of flow (laminar or turbulent) .
  • the high-pressure hydraulic system represented by means of the model M also accounts for the effect of concentrated losses, which damp the pressure waves, by lengthening the tubes by a suitable quantity with respect to their actual lengths.
  • These concentrated losses correspond to the presence of calibrated orifices or to the resistances encountered by the flow of fuel inside the injectors and in the ports of the fuel rail 13 which connect said rail 13 to the injection duct 141. Therefore, given the heterogeneity of the tubes employed in the feed system 1, the resistance Rj is defined, by means of the Poiseuille formulas, in a different manner for each tube as follows:
  • ⁇ and p are respectively the dynamic viscosity and the density of the fuel, so as to make it advantageously possible to model the behavior of the injection system 1 in the presence of fuels of different type and possibly account for thermal effects.
  • the tubes 2, 4, 6 and 8 preferably have circular sections, while the tube 10 preferably has an annular section which is defined by the inner radius R ⁇ n t and outer radius R ex t-
  • R j includes the contribution of the local concentrated resistances, whose effect is taken under consideration by means of the addition of a virtual tube of (reduced) length lj, i oc and internal diameter dj rloc .
  • the model M provides that the tubes do not have hydraulic capacity, the volume V j of each chamber has been increased by a quantity equal to half the (physical) volume of each tube connected to said chamber. In this manner, the reliability of the model M is increased without increasing the complexity thereof, thus allowing the engine control unit 16 to control the quantity of fuel to be injected into the engine in a more precise manner.
  • the hydraulic capacity C 3 can be defined in a manner so as to be a function of the number of injectors of the system 1, so to allow the modeling of multi-injector injection systems advantageously without increasing the number of degrees of freedom (i.e. the size of the state vector) of the model M. From tests carried out by the Applicant, it results that the above-described model M is reliable for providing the trend of the pressure p ra ii in the fuel rail 13 even in multi-injector systems; indeed, since the injectors do not function simultaneously, the injectors which are not active and the relative feed tubes can be modeled by increasing the value of the hydraulic capacity C 3 .
  • the system 1 When the injection system 1 is in an operating condition, said system 1 receives a flow of fuel through the port Pi (Fig. 3) , while it preferably expels two flows of fuel through the ports P 2 and P 3 ;
  • q pump is the mass flow rate supplied by the injection pump 11, while q pv and q ⁇ nj are the flows that exit from the injector respectively through the pilot valve and the injection holes of the nozzle.
  • the flow rates q pU m P , q pv and q in j are the forcing terms of the model with concentrated parameters M and, therefore, they are able to vary the internal fluid-dynamic state of the modeled system M, and hence also that of the (physical) injection system 1.
  • the dynamic behavior of the injection system 1, if such system is linear time-invariant and with concentrated parameters, can be summarized by the following system of formulas:
  • the first vector equation contains the equations present in formulas 1 and 3 expressed in matrix form.
  • the state vector ⁇ x ⁇ is defined in the following manner:
  • the state vector ⁇ x ⁇ is constituted by pressures and flow rates and, since the model M comprises six chambers and five tubes, the state vector ⁇ x ⁇ is a column vector with 11 components
  • the vector ⁇ u ⁇ is the vector containing the external forcing terms that operate on the system and it is defined in the following manner:
  • the matrix A ( [A] e R llx11 ) represents the physical system and includes all the hydraulic capacitances C j , the hydraulic resistances R j and the hydraulic inductances L j ,- such matrix is defined in the following manner:
  • the matrix B ( [B] e 9i llx3 ) defines how the forcing terms ⁇ u ⁇ operate on the physical system, and it is defined in the following manner:
  • the second vector equation of formula 6 is tied to the strategy of control of the injection system 1 employed by the control unit 16; such equation which comprises the terms ⁇ y ⁇ , [C] and [D] , where the vector ⁇ y ⁇ contains the observation variables, i.e. the parameters of the injection system 1 that must be controlled or at least monitored which, in this case, are reduced to the pressure p ra ii of the fuel rail 13, that is
  • the matrix [D] is instead zero, since none of the entering signals relative to the vector ⁇ u ⁇ has an effect on the observation variable p r aii (p3) without simultaneously also modifying the state variables contained in the state vector ⁇ x ⁇ .
  • the transfer function [G(ico)] as defined above can be reformulated in a manner so as to underline the different components that contribute to the observable variable p ra ii in a distinct manner.
  • the relation between the injection flow rate q inj and the pressure p ra ii can be similar to that of a Multi-Input Single Output system (MISO) and, therefore, the transfer function (in the frequency domain) G inj between Q inj and P ra ii ⁇ Qi nj and P ra ii respectively correspond in the frequency domain to g inj (t) and p aiI (t)) can be expressed in the following manner:
  • the function G ⁇ nj is a Single Input Single Output transfer function (SISO) which connects the injected fuel flow rate ⁇ ) ⁇ ⁇ 3 to the pressure of the P ra ii of the fuel rail 13 in the frequency domain (by executing the inverse Fourier transform of P ra ii it is then possible to obtain the trend of p ra ii as a function of time) , while the second expression accounts for the effects that the other two forcing terms, i.e. Q pump and Q pv , have on the injected fuel flow rate Q ⁇ nj .
  • SISO Single Input Single Output transfer function
  • a preferred control system SC which allows the control unit 16 to control the quantity of fuel introduced by the injector 14 into the engine by means of only controlling the pressure of the fuel rail 13.
  • the control system SC receives in inlet the desired flow rates q inj and q pvf and by means of the transfer function G inj such flow rates are used by the engine control unit 16 for computing a reference pressure p ra ii (t) of the fuel rail 13, where t is the time.
  • p ra ii the flow rate of the fuel that flows at its interior on the basis of its number of revolutions n pumPr which is detected by the acquisition means 163 on the injection system 1 (represented in fig.
  • the control unit 16 computes an average deviation £ ra n (also termed error information) between said pressure p ra ii and the pressure p ra ii r ex P detected by the pressure sensor 12 in fig. 1 (represented in fig. 4 by the block HI); after this, the average deviation £ ra n enters into a regulator Rl (implemented by the control unit 16) which, on the basis of said deviation £ ra n, determines whether or not to correct the state of the injector 14 by generating the opportune injector activation signal act in j .
  • a regulator Rl implemented by the control unit 16
  • the regulator Rl can be of PI (Proportional Integral) or PID (Proportional Integral Derivative) type, but it could also be of MPC type or another type. It is evidenced that the teaching provided by this invention does not regard how to make the controller Rl nor how to control the pressure in the rail 13, but rather it regards how to use said controller Rl to control the pressure in the fuel rail 13 as well as the quantity of fuel injected by the injection system 1 into the engine.
  • the flow rate q pv is tied to the flow rate qinj by a transfer function which can be determined with hydraulic test stand of the injectors on the basis of the technical characteristics provided by the manufacturer of the injector 14; therefore, q pv could be computed on the basis of the desired flow rate gi nj and, therefore, the reference pressure p ra ii can be computed on the basis of only the flow rate qinj, since the flow rate q pv is a function of the flow rate qi n j .
  • the engine control unit 16 executes a method for controlling the quantity of injected fuel according to the invention comprising the following phases:
  • o reference information which preferably comprises the reference pressure p ra n or an average value thereof, determined on the basis of a flow rate gi nj or a quantity qty iri j of fuel to be injected into the engine;
  • a first variant is that illustrated in fig. 5 in which the injection system 1' is illustrated; for the sake of brevity in the following description, only the parts which differ this and the subsequent variants with respect to the main embodiment described up to now will be highlighted; for the same reason, the same reference numbers will be used where possible, with one or more primes for indicating elements structurally or functionally equivalent to the new variants.
  • the injection system 1' comprises a control unit 16' similar to the above-described control unit 16 and, as an alternative to or in combination with the valve FMV 17, a pressure control valve 15 installed on the rail (PCV) in signal communication with said control unit 16' and positioned in a manner so as to place the fuel rail 13 in fluid communication with a fuel recovery duct 51 (which has a pressure close to that of the tank 5) when the pressure of the duct reaches a certain pressure threshold.
  • PCV rail
  • the valve 15 (PCV) preferably comprises the following parts:
  • a preload spring which operates on said piston, generating a force capable of overcoming the force generated by the fuel in the rail 13 when this fuel is situated at a pressure typically less than 100 bar (for a Diesel cycle engine) ;
  • This pressure threshold is settable by the control unit 16' and allows varying the level of the nominal pressure p n0 m reachable by the rail 13 so as to make it possible to control the pressure thereof in the injection system.
  • control unit 16' can be used alternatively or in combination with the preceding described embodiment .
  • control system SC will also be described that is similar to the control systems SC previously described in figs. 3 and 4.
  • the control unit 16' is configured in order to execute a model M' (fig. 6) which is similar to the previously described model M, but which additionally models the pressure control valve 15.
  • a model M' (fig. 6) which is similar to the previously described model M, but which additionally models the pressure control valve 15.
  • FMV fuel metering valve
  • a term is added that is considered forcing with respect to the model of the injection system 1, along with a port P 4 through which a fuel flow exits in order to enter into the fuel recovery duct 51, making the trend over time of the pressure p r aii function not just with Qpumpr Qpv and pinjr but also with a pressure control flow rate q P cv that represents the flow rate of fuel which flows through the pressure control valve 15 towards the duct 51.
  • control unit 16' When the injection system 1' is in a certain operating condition, the control unit 16' is capable, preferably by executing a sequence of instructions which implement the model M', of determining the trend of the reference pressure p ra i i on the basis of the flow rates q pump , q pvf q ⁇ n j and q PC v -
  • the unit 16' comprises, in addition to the regulator Rl of the first embodiment, also a second regulator R2 which is configured for generating the valve control signal du tycycl epcv r which actuates, through the actuation means 164, the pressure control valve 15, preferably specifying the position of said valve, on the basis of the pressure p ra ii r ex P detected by the pressure sensor 12 so as to keep the latter as close as possible to a nominal rail pressure p n0m -
  • Such nominal rail pressure p n0m is preferably the ideal work pressure of the injection system 1', i.e. the pressure for which such system 1' was designed and is preferably defined by the injection information; in practice, p n0m can coincide with the average integral of p ra n or with its maximum value.
  • the regulator R2 can be of PI (Proportional Integral) or PID (Proportional Integral Derivative) type, but it could also be of MPC type or of another type.
  • PI Proportional Integral
  • PID Proportional Integral Derivative
  • valve control signal du tycycl e PC v is then read and used, preferably together with the nominal rail pressure p n0m , by the computing means of the unit 16' in order to determine the flow rate q PC v by means of a transfer function H3 preferably implemented by a sequence of instructions which are executed by the computing means 161.
  • transfer function H3 could also be substituted by a flow rate meter configured for measuring the average flow rate of fuel that flows through the pressure control valve 15.
  • the flow rate q PC v is then used by the computing means for computing a reference pressure p ra ii by means of the transfer function Gi nj ' reported above.
  • transfer function Gi nj ' takes into account the transfer function G PC v of the pressure control valve 15 and the trend of the flow rate through said valve 15 in the frequency domain .
  • the presence of the PCV ensures an improved dynamic response of the injection system during engine transients with respect to the case of the FMV, making possible an accurate control of the fuel quantity injected by the injector 14, with respect to the case of the FMV.
  • a third embodiment of a control unit 16'' according to the invention will now be described; such apparatus 16'' is comprised in a control system SC' and differs from the units 16 and 16' of the preceding embodiments with regard to the computation of the error information. This is made not on the basis of the reference pressure (generated by the transfer function G in j) and the pressure p ra ii r ex P of the fuel rail, but rather on the basis of the desired flow rate qinj (which is included, as with the other embodiments, in the injection information) and of an estimated flow rate q ⁇ n j*.
  • the flow rate q ⁇ n j* is estimated by means of a transfer function F ln1 reported below:
  • F inj allows estimating the flow rate q ⁇ n j* of fuel injected by the injector 14 on the basis of the forcing terms q pU m P , Praii r ex P and (optionally) q pv (in the frequency domain Q pump , P ra ii r ex P and Q PV ) ; such terms are determined/detected as in the second embodiment of the invention, i.e. p ra ii r ex P is detected by means of a pressure sensor 12 (represented in fig.
  • q pump is determined by means of a transfer function H2 which allows computing said flow rate q pU m P on the basis of the number of revolutions n pump of the injection pump 11 and possibly of p while q pv is for example determined on the basis of a transfer function which can be determined on the basis of the technical characteristics provided by the manufacturer of the injector 14.
  • the transfer function F in - can also be obtained by solving the formula 14'
  • the control unit 16' ' computes an average deviation £inj between said flow rate of fuel to be injected q inj and the flow rate q ⁇ n j* estimated by means of the function F inj ; after this, the average deviation £ inj enters into a regulator R3 (implemented by the control unit 16' ') which, on the basis of said deviation Sinj, determines the activation signal acti nj that operates on the injector 14.
  • the regulator R3 can be of PI (Proportional Integral) or PID (Proportional Integral Derivative) type, but it could also be of MPC type or another type. It is evidenced that the teaching provided by this invention does not regard how to make the controller R3, but rather how to use said controller R3 for controlling the quantity of fuel injected by the injection system 1 into the engine.
  • This embodiment allows varying the flow rate of injected fuel in a quicker manner with respect to the preceding embodiments, i.e. it is able to reduce the time between a variation of the desired flow rate gi nj and the consequent activation or deactivation (or correction of the energization time) of the injector 14, thus improving the control of the quantity of injected fuel; indeed, the unit 16'' carries out the computing of the estimated flow rate q ⁇ n j* downstream of the feedback branch, in a manner so as to reduce the response time to a variation of the desired flow rate qinj, since the reference signal qi n j does not have to first be transformed into pressure, as instead occurs for the previously described embodiments, but it is the feedback signal that is transformed by means of an opportune transfer function into a value of flow rate qi n j* comparable with that of the desired flow rate
  • a fourth embodiment of a control unit 16''' according to the invention will now be described; such apparatus 16' ' ' is comprised in a control system SC ' ' and differs from the units 16'' of the preceding embodiment just described above due to the possibility of computing a piece of error information £ qty inj - not on the basis of the desired flow rate q in j and an estimated flow rate qinj*, but rather on the basis of the quantity to be injected qty inj (integral over time of qinj) r preferably in the course of an operation cycle or of a single injection, and the estimated injected quantity qty in j* (integral over time of q ⁇ n j*) , preferably in the course of the same operation cycle or of the same single injection.
  • the control unit 16''' computes a deviation £ gty _i nj between said quantity of fuel to be injected qty in j and the estimated quantity qtyin j * by means of the integration in a time interval of the result of the function q in j* (which is obtained by anti- trans forming the function Qinj*) , i.e. of the estimated flow rate; after this, the average deviation £ inj enters into a regulator R4 (implemented by the control unit 16''') which, on the basis of said deviation £ qty in j, determines whether or not to activate the injector (e.g. by correcting the energization time ET of the injector) 14, by generating the injector activation signal act in j ⁇
  • the regulator R4 can be PI (Proportional Integral) or PID (Proportional Integral Derivative) type, but it could also be of MPC type or another type. It is evidenced that the teaching provided by this invention does not regard how to make the controller R4, but rather it regards how to use said controller R4 to control the quantity of fuel injected by the injection system 1 into the engine.
  • the processing and control means 161 of the apparatus 16''' are configured for determining the quantity to be injected tyinj on the basis of at least the injection information, and for determining the estimated injected quantity qty in j* by computing the integral over time (e.g. by means of a summation operation) of the estimated flow rates qinj* by means of the transfer function F lnj .
  • the value of estimated injected quantity qty in j* is representative of only one operation cycle of the propulsor or of a single injection, such integration operation must preferably start from the beginning of each injection or at least of each operation cycle of the propulsor; for such purpose, the value of the estimated injected quantity qty in j* r which is obtained by means of process of integration of the estimated flow rate qinj*, must be zeroed at the start of each injection or at least of each propulsor operation cycle, e.g. by generating an initialization signal RST.
  • This embodiment allows defining the quantities of fuel to be injected in a simpler manner with respect to the preceding embodiments, since the control system SC ' ' controls the quantity of fuel to be injected and no longer controls the fuel flow rate. In this manner, the generation of the injection information is simplified, thus simplifying the adjustment of the propulsor.
  • the spectral model is obtainable starting from a series of measurements obtained by means of a test stand of the injectors, wherein each measurement comprises a duct pressure measurement and a flow rate measurement, and wherein all the pressure and flow rate measurements respectively form the (point) functions in the time domain p(t) (equivalent to
  • W T (t) is a window function, preferably the Hanning window function
  • T is a time interval much smaller than the rotation period of the injection pump 11 (which is preferably equal to double the rotation period of the internal combustion engine fed by the injection system 1,1')
  • K is the number of window functions that one wishes to use
  • At ov is the superimposition time for two subsequent windows, which is preferably greater than half the time interval T.
  • ⁇ ⁇ ( ⁇ ) ⁇ _ + ⁇ ⁇ ( ⁇ ) ⁇ - ⁇ ⁇
  • _R PP is the autocorrelation function of p w (t)
  • R qq is the autocorrelation function of q w (t)
  • R pq and -R gp are the cross- correlation functions between p w (t) and q diary(t) and T d is the integration domain.

Abstract

L'invention concerne un appareil et un procédé qui permettent de commander la quantité de carburant injecté dans un moteur à combustion interne, ledit appareil (16) comprenant un moyen d'acquisition (163) conçu pour acquérir une pression de rampe à carburant ((p rail,exp ), un moyen d'actionnement (164) conçu pour générer au moins un signal d'injection (actinj) qui actionne un injecteur, un moyen de traitement et de commande (161) conçu pour calculer au moins un élément d'information d'erreur (P raiI ) sur la base d'au moins une information de référence (praii) déterminée sur la base d'un débit d'écoulement (q inj ) ou d'une quantité de carburant à injecter dans le moteur, et d'informations de rétroaction déterminées sur la base de la pression de rampe à carburant (P rail,exp ), ledit moyen de traitement et de commande (161) étant également conçu pour faire varier la pression de rampe à carburant (P rail,exp ) par le moyen d'actionnement (164) de manière à maintenir l'amplitude de l'information d'erreur (ε rail ) en dessous d'un seuil.
PCT/IB2016/057601 2015-12-16 2016-12-14 Appareil et procédé pour réguler la quantité de carburant injecté dans un moteur à combustion interne WO2017103803A1 (fr)

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IT202100026006A1 (it) 2021-10-11 2023-04-11 Torino Politecnico Sistema di iniezione con efficiente controllo in quantità iniettata

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IT202100026006A1 (it) 2021-10-11 2023-04-11 Torino Politecnico Sistema di iniezione con efficiente controllo in quantità iniettata
CN114893315A (zh) * 2022-04-11 2022-08-12 哈尔滨工程大学 一种基于在线感知为基础的高压共轨燃油喷射器燃油喷射量控制系统及其mpc闭环

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