INTERNAL COMBUSTION ENGINE WITH INJECTION AMOUNT CONTROL

Abstract

A combustion engine with at least one injector for the injection of liquid fuel into at least one combustion chamber is provided. The injector can be regulated by means of a regulating device through an actuator triggering signal, wherein the at least one injector has an outlet opening that can be closed by means of a needle. An algorithm is contained in the regulating device, which receives as an input value at least the actuator trigger signal, and which calculates via an injector model the mass of liquid fuel transferred via the outlet opening of the injector. The regulating device compares by means of the injector model, the calculated mass with a required target value ref of the mass of liquid fuel, to correct the actuator trigger signal.

Claims

1. A combustion engine comprising: a regulating device, at least one combustion chamber; and at least one injector that can be regulated through a regulating device via an actuator trigger signal for injecting liquid fuel into the at least one combustion chamber, with the at least one injector possessing an exit opening for liquid fuel that can be closed by a needle; wherein the regulating device incorporates an algorithm, receives as an input value at least the actuator trigger signal, using an injector model calculates the mass of the liquid fuel emitted from the exit opening of the injector, compares the mass calculated by the injector model with a required target value of the mass of the liquid fuel, and depending on the result of such comparison, leaves the actuator trigger signal unchanged or corrects the actuator trigger signal.

2. The combustion engine in accordance with claim 1, wherein the algorithm possesses a preliminary control which, on the basis of the required target value for the mass of the liquid fuel calculates a preliminary control signal for the actuator trigger signal for the injection duration.

3. The combustion engine in accordance with claim 1, wherein at least one sensor is provided in, or can be brought into, signal connection with the regulating device, through which at least one measurement value of the at least one injector can be measured by the sensor.

4. The combustion engine in accordance with claim 3, wherein the algorithm possesses a feedback loop which uses a preliminary signal calculated by a preliminary control system for the actuator trigger signal for the injection duration, and the at least one measurement value, calculates a volume of the liquid fuel issued via the exit opening of the injector, using the injector model and, if necessary, corrects the preliminary control signal for the injection duration as calculated by the preliminary control system using a correction value.

5. The combustion engine in accordance with claim 1, wherein the algorithm possesses an observer function which, by using the injector model, the actuator trigger signal, and the at least one measurement value, estimates the injector mass of the liquid fuel.

6. The combustion engine in accordance with claim 1, wherein the injector model contains at least: pressure progressions in volumes of the injector filled with the liquid fuel; mass flow rates between the volumes of the injector filled with the liquid fuel; a position of the needle with relation to a needle seat; and dynamics of the actuator of the needle.

7. The combustion engine in accordance with claim 1, wherein the injector possesses at least: one input accumulator chamber connected with one Common-Rail of the combustion engine; one accumulator chamber for the liquid fuel, connected with the input accumulator chamber; one volume above the needle seat connected with the accumulator chamber; one connection volume connected on one side with the accumulator chamber and on an other side with an outflow duct; one output opening for the liquid fuel that can be closed by the needle and which is connected with a volume above the needle seat; one actuator that can be triggered by an actuator triggering signal for opening the needle; and one control chamber joined on one side to the accumulator chamber and on an other side to the connection volume.

8. The combustion engine in accordance with claim 1, wherein at least one measurement value is selected from the following values or a combination thereof: pressure of one Common-Rail of the combustion engine; pressure in one input accumulator chamber of the injector; pressure in one control chamber of the injector; and commencement of lift-off of the needle from a needle seat.

9. The combustion engine in accordance with claim 1, wherein the regulating device carries out the algorithm during each combustion cycle, or during selected combustion cycles of the combustion engine and corrects the actuator triggering signal during such combustion cycle, in case of deviations.

10. The combustion engine in accordance with claim 1, wherein the regulating device carries out the algorithm during each combustion cycle or during selected combustion cycles of the combustion engine, and in case of deviations, corrects the actuator triggering signal in a subsequent combustion cycle.

11. The combustion engine in accordance with claim 1, wherein the regulating device carries out the algorithm during each combustion cycle or during selected combustion cycles of the combustion engine and statically evaluates any deviations occurring, and carries out a correction of the actuator triggering signal for the current or for a subsequent combustion cycle based on the static evaluation.

12. A process for operation of the combustion engine in accordance with claim 1, comprising: transferring the liquid fuel to a combustion chamber of the combustion engine, calculating the mass of the liquid fuel fed into the combustion chamber through use of the injector model based on the actuator trigger signal for an actuator of the injector for the liquid fuel and in which the actuator trigger signal is corrected in case of deviations between a target value for the mass of the liquid fuel and the calculated mass.

13. A process for operating an injector comprising: injecting liquid fuel into a combustion chamber of a combustion engine; and calculating a mass of the liquid fuel fed into the combustion chamber by the injector using an injector model based on an actuator trigger signal of an actuator of the injector for the liquid fuel, with the actuator trigger signal corrected in case of deviations between a target value for the mass of the liquid fuel and the calculated mass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Examples of embodiments of the disclosure are explained using figures, which show:

[0045] FIG. 1 a first embodiment of the regulating system diagram;

[0046] FIG. 2 a second embodiment of the regulating system diagram;

[0047] FIG. 3 a first example of a schematically represented injector; and

[0048] FIG. 4 a second example of a schematically represented injector.

DETAILED DESCRIPTION

[0049] FIG. 1:

[0050] The purpose of the injector regulation in this embodiment is the regulation of the actually injected mass of liquid fuel to a target value m.sub.d.sup.ref, by controlling the injection duration t. The regulation strategy is carried out by:

[0051] a preliminary control (FF), which uses a required target value m.sub.d.sup.ref for the mass of liquid fuel to calculate a preliminary control signal t.sub.ff (also referred to below as control command) for the injection duration .sub.t and

[0052] a feedback loop (FB), which by using an observer system 7 (State Estimator) takes into account the control command, calculated by the precontrol system, for the injection duration .sub.t and at least one measurement value y (e.g. one of the pressure progressions P.sub.IA, P.sub.CC, P.sub.JC, P.sub.AC, P.sub.SA, occurring in the injector or the commencement of the lift-off of the needle from the needle seat) estimates, by means of the injector model, the mass flow {circumflex over (m)}.sub.d of liquid fuel introduced through the output opening of the injector and, where required, corrects the target value t.sub.ff calculated by the preliminary control for the injection duration by using a correction value t.sub.fb (which may be negative).

[0053] The preliminary control ensures a fast system response, since it triggers the injector with an injection duration t.sub.ff as though no injector variability existed. The preliminary control uses a calibrated field of injector characteristics (which determines the current supply duration via the injection mass or volume) or to convert the inverted injector model into the preliminary control command t.sub.ff for the injection duration using the target value m.sub.d.sup.ref for the mass of liquid fuel.

[0054] The feedback loop (FB) is used in order to correct any inaccuracies in the preliminary control system (due to manufacturing variability, wear, etc.), which cause injector drift. The feedback loop compares the target value m.sub.d.sup.ref with the estimated injected mass {circumflex over (m)}.sub.d of liquid fuel and gives as a feedback a correcting control command for the injection duration t.sub.fb if there is any discrepancy between m.sub.d.sup.ref and {circumflex over (m)}.sub.d. The addition of t.sub.ff and t.sub.fb or gives the definitive injection duration t.

[0055] The observer system estimates the injected mass {circumflex over (m)}.sub.d of liquid fuel depending on the at least one measurement value y and the final injection duration t. The at least one measurement value y can, for example, refer to: common rail pressure P.sub.CR, pressure in the input accumulation chamber P.sub.IA, pressure in the control chamber P.sub.CC or the commencement of the lift-off of the needle from the needle seat. The observer system uses a reduced injector model in order to estimate the injected mass {circumflex over (m)}.sub.d of liquid fuel.

[0056] FIG. 2:

[0057] This figure shows a regulating system composed of a single part (without a preliminary control command t.sub.ff) in which the actuator trigger signal .sub.t is calculated on the basis of the target value m.sub.d.sup.ref for the injected mass of liquid fuel and on the basis of the parameter par.sub.mod which is estimated by the observer function and used in the preliminary control model. In this way, an adaptive preliminary control signal is obtained that is modified by the observer.

[0058] Hence, in this case, the regulating system is not composed in two parts, with a preliminary control and a feedback loop that corrects the preliminary control signal.

[0059] FIG. 3 shows a block diagram for a reduced injector model. The injector model consists of a structural model for the injector and a system of equations for describing the dynamic behavior of the structural model. The structural model consists of five modeled volumes: Intake accumulator 1, accumulator chamber 3, control chamber 2, volume above the needle seat and connection volume 5.

[0060] The intake accumulator chamber 1 represents the accumulation of all the volumes between the input choke and the non-return valve. The accumulator chamber 3 represents the combination of all volumes from the non-return valve to the volume above the needle seat. The volume above the needle seat represents a combination of all volumes between the needle seat up to the output opening of the injector. The connection volume 5 represents the combination of all the volumes, which connect the volumes of the accumulator chamber 3 and the control chamber 2 with the solenoid valve.

[0061] FIG. 4 shows an alternative injector design, which succeeds in functioning without a control chamber, e.g. an injector in which the needle is triggered by a Piezo element.

[0062] The following system of equations does not refer to the version shown in FIG. 4. The formulation of a suitable equation system can be carried out analogously to the equation system shown below.

[0063] The dynamic behavior of the structural model is described through the following equation system:

[0064] Pressure Dynamics

[0065] The development through time of the pressure within each of the volumes is calculated on the basis of a combination between the mass conservation equation and the pressure-density characteristic of the liquid fuel. The progression through time of the pressure is determined by:

[00001]$\begin{array}{cc}{\stackrel{.}{p}}_{\mathrm{IA}}=\frac{K_f}{{}_{\mathrm{IA}}.Math.V_{\mathrm{IA}}}.Math.\left({\stackrel{.}{m}}_{i.Math..Math.n}-{\stackrel{.}{m}}_{\mathrm{aci}}\right)& \mathrm{EQ}..Math.1.1\\ {\stackrel{.}{p}}_{\mathrm{CC}}=\frac{K_f}{{}_{\mathrm{CC}}.Math.V_{\mathrm{CC}}}.Math.\left({\stackrel{.}{m}}_{\mathrm{zd}.Math.}-{\stackrel{.}{m}}_{\mathrm{ad}}-{}_{\mathrm{CC}}.Math.{\stackrel{.}{V}}_{\mathrm{CC}}\right)& \mathrm{EQ}..Math.1.2\\ {\stackrel{.}{p}}_{\mathrm{jC}}=\frac{K_f}{{}_{\mathrm{JC}}.Math.V_{\mathrm{JC}}}.Math.\left({\stackrel{.}{m}}_{\mathrm{bd}}+{\stackrel{.}{m}}_{\mathrm{ad}}-{\stackrel{.}{m}}_{\mathrm{sol}}\right)& \mathrm{EQ}..Math.1.3\\ {\stackrel{.}{p}}_{A.Math..Math.C}=\frac{K_f}{{}_{A.Math..Math.C}.Math.V_{A.Math..Math.C.Math.}}.Math.\left({\stackrel{.}{m}}_{\mathrm{aci}}-{\stackrel{.}{m}}_{\mathrm{ann}}-{\stackrel{.}{m}}_{\mathrm{bd}}-{\stackrel{.}{m}}_{\mathrm{zd}}-{}_{A.Math..Math.C}.Math.{\stackrel{.}{V}}_{A.Math..Math.C}\right)& \mathrm{EQ}..Math.1.4\\ {\stackrel{.}{p}}_{\mathrm{SA}}=\frac{K_f}{{}_{\mathrm{SA}}.Math.V_{\mathrm{SA}}}.Math.\left({\stackrel{.}{m}}_{\mathrm{ann}}-{\stackrel{.}{m}}_{\mathrm{inj}}-{}_{\mathrm{SA}}.Math.{\stackrel{.}{V}}_{\mathrm{SA}}\right)& \mathrm{EQ}..Math.1.5\end{array}$

[0066] Symbols used in the formulae [0067] P.sub.IA: Pressure in the intake accumulator chamber 1 in bar [0068] P.sub.CC: Pressure in the control chamber 2 in bar [0069] P.sub.JC: Pressure in the junction volume 5 in bar [0070] P.sub.AC: Pressure in the accumulator chamber 3 in bar [0071] P.sub.SA: Pressure in the small accumulator chamber 4 in bar [0072] P.sub.IA: Diesel mass density within the intake accumulator chamber 1 in kg/m.sup.3 [0073] P.sub.CC: Diesel mass density within the control chamber 2 in kg/m/.sup.3 [0074] P.sub.JC: Diesel mass density within the junction volume 5 in kg/m.sup.3 [0075] P.sub.AC: Diesel mass density within the accumulation chamber 3 in kg/m.sup.3 [0076] P.sub.SA: Diesel mass density within the small accumulator chamber 4 in kg/m.sup.3 [0077] K.sub.f: Compression modulus of the Diesel fuel in bar

[0078] Needle Dynamics

[0079] The needle position is calculated by means of the following movement equation:

[00002]$\begin{array}{cc}\stackrel{\mathrm{.Math.}}{z}=\{\begin{array}{c}0.Math..Math.\mathrm{if}.Math..Math.F_{\mathrm{hyd}}{F}_{\mathrm{pre}}\\ \frac{1}{m}.Math.\left(F_{\mathrm{hyd}}-\mathrm{Kz}-B.Math.\stackrel{.}{z}-F_{\mathrm{pre}}\right).Math..Math.\mathrm{if}.Math..Math.F_{\mathrm{hyd}}>F_{\mathrm{pre}}\end{array}& \mathrm{EQ}..Math.2.1\\ F_{\mathrm{hyd}}=p_{A.Math..Math.C}.Math.A_{A.Math..Math.C}+p_{\mathrm{SA}}.Math.A_{\mathrm{SA}}-p_{\mathrm{CC}}.Math.A_{\mathrm{CC}}& \mathrm{EQ}..Math.2.2\\ 0z{z}_{\mathrm{ma}.Math..Math.x}& \mathrm{EQ}..Math.2.3\end{array}$

[0080] Symbols used in the formulae: [0081] z: Needle position in meters (m) [0082] z.sub.max: Maximum displacement of the needle 6 in m [0083] k: Stiffness of spring in N/m [0084] B: Spring damping co-efficient in N.s/m [0085] F.sub.pre: Spring pretension in N [0086] A.sub.AC: Hydraulic effective area in the accumulator chamber 3 in m.sup.2 [0087] A.sub.SA: Hydraulic effective area in the small accumulator chamber 4 in m.sup.2 [0088] A.sub.CC: Hydraulic effective area in the control chamber 2 in m.sup.2

[0089] Dynamics of the Solenoid Valve

[0090] The solenoid valve is modeled through a first order transfer function, which converts the valve opening command into a valve position. This is provided by:

[00003]$\stackrel{u_{\mathrm{sol}}^{\mathrm{cmd}}}{}.Math.\frac{z_{\mathrm{sol}}^{m.Math..Math.\mathrm{ax}}}{{}_{\mathrm{sol}}.Math.s+1}.Math.\stackrel{z_{\mathrm{sol}}}{}$

[0091] The transient system behavior is characterized by the time constant t.sub.sol and the position of the needle 6 at maximum valve opening is given by Z.sup.max/.sub.sol 1. A piezo-electric operation is also possible instead of a solenoid valve.

[0092] Mass Flow Rates

[0093] The mass flow rate through each valve is calculated using the standard choked flow equation for liquids, which is:

[00004]$\begin{array}{cc}{\stackrel{.}{m}}_{i.Math..Math.n}=A_{i.Math..Math.n}.Math.C_{\mathrm{din}}.Math.\sqrt{2.Math.{}_j.Math..Math.p_{\mathrm{Ck}}-p_{\mathrm{iA}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{CR}}-p_{\mathrm{iA}}\right)& \mathrm{EQ}..Math.3.1\\ {\stackrel{.}{m}}_{\mathrm{bd}}=A_{\mathrm{bd}}.Math.C_{\mathrm{dbd}}.Math.\sqrt{2.Math.{}_j.Math..Math.p_{A.Math..Math.C}-p_{\mathrm{jC}}.Math.}.Math.\mathrm{sgn}\left(p_{A.Math..Math.C}-p_{\mathrm{jC}}\right)& \mathrm{EQ}..Math.3.2\\ {\stackrel{.}{m}}_{\mathrm{zd}}=A_{\mathrm{zd}}.Math.C_{\mathrm{dzd}}.Math.\sqrt{2.Math.{}_j.Math..Math.p_{A.Math..Math.C}-p_{\mathrm{CC}}.Math.}.Math.\mathrm{sgn}\left(p_{A.Math..Math.C}-p_{\mathrm{CC}}\right)& \mathrm{EQ}..Math.3.3\\ {\stackrel{.}{m}}_{\mathrm{ad}}=A_{\mathrm{ad}}.Math.C_{\mathrm{dad}}.Math.\sqrt{2.Math.{}_j.Math..Math.p_{\mathrm{CC}}-p_{\mathrm{jC}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{CC}}-p_{\mathrm{jC}}\right)& \mathrm{EQ}..Math.3.4\\ {\stackrel{.}{m}}_{\mathrm{sol}}=A_{\mathrm{sol}}.Math.C_{\mathrm{dsol}}.Math.\sqrt{2.Math.{}_j.Math..Math.p_{\mathrm{jC}}-p_{\mathrm{LP}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{jC}}-p_{\mathrm{LP}}\right)& \mathrm{EQ}..Math.3.5\\ {\stackrel{.}{m}}_{\mathrm{aci}}=A_{\mathrm{aci}}.Math.C_{\mathrm{deci}}.Math.\sqrt{2.Math.{}_j.Math..Math.p_{\mathrm{iA}}-p_{A.Math..Math.C}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{iA}}-p_{A.Math..Math.C}\right)& \mathrm{EQ}..Math.3.6\\ {\stackrel{.}{m}}_{\mathrm{ann}}=A_{\mathrm{ann}}.Math.C_{\mathrm{dmn}}.Math.\sqrt{2.Math.{}_j.Math..Math.p_{A.Math..Math.C}-p_{\mathrm{SA}}.Math.}.Math.\mathrm{sgn}\left(p_{A.Math..Math.C}-p_{\mathrm{SA}}\right)& \mathrm{EQ}..Math.3.7\\ {\stackrel{.}{m}}_{\mathrm{inj}}=A_{\mathrm{inj}}.Math.C_{\mathrm{dinj}}.Math.\sqrt{2.Math.{}_{\mathrm{SA}}.Math..Math.p_{\mathrm{SA}}-p_{\mathrm{cyl}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{SA}}-p_{\mathrm{cyl}}\right)& \mathrm{EQ}..Math.3.8\\ {}_j=\{\begin{array}{c}{}_{i.Math..Math.n}.Math..Math.\mathrm{if}.Math..Math.p_{i.Math..Math.n}{p}_{\mathrm{out}}\\ {}_{\mathrm{out}}.Math..Math.\mathrm{if}.Math..Math.p_{i.Math..Math.n}<p_{\mathrm{out}}\end{array}& \mathrm{EQ}..Math.3.9\end{array}$

[0094] Formula symbols used: [0095] {dot over (m)}.sub.in: Mass flow density through the input choke in kg/s [0096] {dot over (m)}.sub.bd: Mass flow rate via the bypass valve between accumulator chamber 3 and junction volume 5 in kg/s [0097] {dot over (m)}.sub.zd: Mass flow rate via feeder valve at the entry point of the control chamber 3 in kg/s [0098] {dot over (m)}.sub.ad: Mass flow rate via the discharge valve from control chamber 2 in kg/s [0099] {dot over (m)}.sub.sol: Mass flow rate via the solenoid valve in kg/s [0100] {dot over (m)}.sub.aci: Mass flow rate via the entry point into the accumulator chamber 3 in kg/s [0101] {dot over (m)}.sub.ann: Mass flow rate via the needle seat in kg/s [0102] {dot over (m)}.sub.inj: Mass flow rate via the injector jet in kg/s

[0103] On the basis of the injector model formulated above, the expert will obtain the estimated value and by means of the observer system in a manner which is in principle already known (see e.g. B. Iserman, Rolf, Digitale Regelsysteme [Digital control systems], Springer Verlag Heidelberg 1977, Chapter 22.3.2, Page 379 et seq. or F. Castillo et al. Simultaneous Air Fraction and Low-Pressure EGR Mass Flow Rate Estimation for Diesel Engines, IFAC Joint conference SSSC5th Symposium on System Structure and Control, Grenoble, France 2013).

[0104] By using the above system of equations, it is possible to construct the so-called observer equations, making use of an observer system which is known in principle, of the sliding mode observer type, by adding to the equations in the injector model the so-called observer law. For a sliding mode observer, one obtains the observer law by calculating a hypersurface using the at least one measurement signal and the value that results from the observer equations. By squaring the equation for the hypersurface, one obtains a generalized Lyapunov equation (generalised energy equation). This is a functional equation. The observer law represents that function which is minimized by the functional equation. This can be determined by variation techniques, which are known in principle, or numerically. This process is carried out within a combustion cycle for each step in time (depending on the time resolution of the control system).

[0105] Depending on the application, the result is the estimated injected mass of liquid fuel, the position of needle 6 or one of the pressures in one of the volumes of the injector.

[0106] This written description uses examples to disclose preferred embodiments, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.