INTERNAL COMBUSTION ENGINE HAVING AN INJECTION AMOUNT CONTROL

Abstract

An internal combustion engine including a control device, at least one combustion chamber, and at least one injector for injecting liquid fuel into the at least one combustion chamber is provided. The injector can be controlled by the control device by means of an actuator control signal. An algorithm is stored in the control device, which algorithm receives the actuator control signal and using an injector model calculates the amount of liquid fuel that is discharged via the discharge opening of the injector and compares the amount of liquid fuel calculated by means of the injector model with a desired target value of the amount of liquid fuel. Depending on the result of the comparison, the control device leaves the actuator control signal the same or corrects it.

Claims

1. An internal combustion engine comprising: a control device; at least one combustion chamber; and at least one injector for injecting liquid fuel into the at least one combustion chamber, the at least one injector controlled by the control device by means of an actuator control signal, wherein the at least one injector comprises a discharge opening for the liquid fuel which can be closed by a needle; wherein an algorithm is stored in the control device, which receives as an input variable at least the actuator control signal and using an injector model calculates an amount of liquid fuel discharged via the discharge opening of the injector and compares the amount of liquid fuel calculated by means of the injector model with a desired target value of the amount of liquid fuel and depending on the result of the comparison, leaves the actuator control signal the same or corrects it; wherein the injector comprises at least: an input storage chamber connected to a common rail of the internal combustion engine, a storage chamber for the liquid fuel connected to the input storage chamber, a volume connected over a needle seat to the storage chamber; a connection volume connected on one side to the storage chamber and on an other side to a drain line; the discharge opening for the liquid fuel, which can be closed by the needle and is connected to the volume over the needle seat; an actuator controllable by means of the actuator control signal for opening the needle; the control chamber connected on one side to the storage chamber and on the other side to the connection volume; and the injector model comprises at least: pressure progressions in the input storage chamber, the storage chamber, the volume over the needle seat and the connection volume; mass flow rates between the input storage chamber, the storage chamber, the volume over the needle seat and the connection volume; a position of the needle, preferably relative to the needle seat; and dynamics of the actuator of the needle.

2. The internal combustion engine according to claim 1, wherein the algorithm comprises a pilot control, which from the desired target value of the amount of liquid fuel calculates a pilot control signal for the actuator control signal for the injection duration.

3. The internal combustion engine according to claim 1, wherein at least one sensor is provided, by which at least one measurement variable of the at least one injector can be measured, wherein the sensor is in, or can be brought into, a signal connection with the control device.

4. The internal combustion engine according to claim 3, wherein the algorithm comprises a feedback loop, which, based on the actuator control signal calculated by the pilot control for the injection duration and the at least one measurement variable, calculates the amount of liquid fuel discharged via the discharge opening of the injector by means of an injector model and, if necessary, corrects the target value for the injection duration.

5. The internal combustion engine according to claim 1, wherein the algorithm comprises an observer, which, using the injector model and based on the actuator control signal and the at least one measurement variable, estimates the injected amount of liquid fuel.

6. The internal combustion engine according to claim 1, wherein the at least one measurement variable is selected from the following variables or a combination thereof: pressure in the common rail of the internal combustion engine; pressure in the input storage chamber of the injector; pressure in the control chamber of the injector; and start of the needle lift-off from the needle seat.

7. The internal combustion engine according to claim 1, wherein the control device is designed to execute the algorithm during each combustion cycle or selected combustion cycles of the internal combustion engine and to correct the actuator control signal in the case of deviations during this combustion cycle.

8. The internal combustion engine according to claim 1, wherein the control device is designed to execute the algorithm during each combustion cycle or selected combustion cycles of the internal combustion engine and in case of deviations to correct the actuator control signal in one of the subsequent combustion cycles.

9. The internal combustion engine according to claim 1, wherein the control device is designed to execute the algorithm during each combustion cycle or selected combustion cycles of the internal combustion engine and to statically evaluate the deviations that have occurred and to make a correction of the actuator control signal for this or one of the subsequent combustion cycles in accordance with the static evaluation.

10. The internal combustion engine according to claim 1, wherein at least one gas supply device for the supply of a gaseous fuel to the at least one combustion chamber is provided and the internal combustion engine is designed as a dual-fuel internal combustion engine.

11. A method for operating the internal combustion engine according to claim 1, comprising: supplying the at least one combustion chamber of the internal combustion engine with the liquid fuel, wherein the amount of liquid fuel supplied to the at least one combustion chamber is calculated depending on the actuator control signal of the actuator of the injector for the liquid fuel and a measurement variable of the injector by using the injector model, and the actuator control signal is corrected in the event of deviations between the target value for the amount of liquid fuel and the calculated amount.

12. A method for operating an injector, comprising: injecting with the injector an amount of liquid fuel into a combustion chamber of an internal combustion engine; wherein the amount of liquid fuel supplied to the combustion chamber is calculated depending on an actuator control signal of an actuator of the injector for the liquid fuel by using an injector model, and wherein the actuator control signal is corrected in case of deviations between a target value for the amount of liquid fuel and the calculated amount.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Exemplary embodiments of the invention will be explained with reference to the figures. They are as follows:

[0035] FIG. 1 a first exemplary embodiment of the control scheme;

[0036] FIG. 2 a second exemplary embodiment of the control scheme;

[0037] FIG. 3 a first example of a schematically illustrated injector; and

[0038] FIG. 4 a second example of a schematically illustrated injector.

DETAILED DESCRIPTION

[0039] It should be noted that the gas supply device for the supply of gaseous fuel to the at least one combustion chamber (apart from the schematically represented valves) or the corresponding control or regulation are shown in none of the figures. They correspond to the state of the art.

[0040] FIG. 1:

[0041] The object of the injector control in this exemplary embodiment is the control of the actual injected amount of liquid fuel to a target value m.sub.d.sup.ref, by controlling the injection duration t. The control strategy is performed by a pilot control (FF), which calculates, from a desired target value m.sub.d.sup.ref for the amount of liquid fuel, a pilot control signal t.sub.ff (hereinafter also referred to as control command) for the injection duration t, and a feedback loop (FB) which, using an observer 7 (state estimator) and taking into account the control command calculated by the pilot control for the injection duration t and at least one measurement variable 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 start of the lift-off from the needle seat) estimates the mass flow {circumflex over (m)}.sub.d of liquid fuel discharged via the discharge opening of the injector by means of an injector model and, if necessary, corrects the target value t.sub.ff calculated by the pilot control for the injection duration to the actual duration of the actuator control signal t by means of a correction value t.sub.fb (which can be negative).

[0042] The pilot control ensures a fast system response, since it controls the injector with an injection duration t as if no injector variability existed. The pilot control uses a calibrated injector map (which indicates the duration of current flow over the injection amount or volume) or the inverted injector model to convert the target value m.sub.d.sup.ref of the amount of liquid fuel into the pilot control command t.sub.ff for the injection duration.

[0043] The feedback loop (FB) is used to correct the inaccuracies of the pilot control (due to manufacturing variabilities, wear, etc.), which cause an injector drift. The feedback loop compares the target value m.sub.d.sup.ref with the estimated injected amount of liquid fuel {circumflex over (m)}.sub.d and gives as feedback a correction control command t.sub.fb for the injection duration, if there is a discrepancy between m.sub.d.sup.ref and {circumflex over (m)}.sub.d. The addition of t.sub.ff and t.sub.fb gives the final injection duration t.

[0044] The observer estimates the injected amount {circumflex over (m)}.sub.d of liquid fuel, which is dependent on the at least one measurement variable y and the final injection duration t. The at least one measurement variable y can refer to: common rail pressure p.sub.CR, pressure in the input storage chamber p.sub.IA, pressure in the control chamber p.sub.CC, and the start of the needle lift-off from the needle seat. The observer uses a reduced injector model to estimate the injected amount {circumflex over (m)}.sub.d of liquid fuel.

[0045] FIG. 2:

[0046] This figure shows a one-piece control (without pilot control command t.sub.ff), in which the actuator control signal .sub.t is calculated based on the target value m.sub.d.sup.ref for the injected amount of liquid fuel and based on the parameter gar.sub.mod used in the pilot control model and estimated by the observer. In this way, an adaptive pilot control signal, modified by the observer, is obtained. In this case, the control is therefore not composed of two parts, with a pilot control and a feedback loop which corrects the pilot control signal.

[0047] FIG. 3 shows a block diagram of a reduced injector model. The injector model consists of a structural model of the injector and an equation system to describe the dynamic behavior of the structural model. The structural model consists of five modeled volumes: input storage chamber 1, storage chamber 3, control chamber 2, volume over needle seat and connection volume 5.

[0048] The input storage chamber 1 represents the summary of all volumes between the input throttle and the check valve. The storage chamber 3 represents the summary of all volumes from the check valve to the volume above the needle seat. The volume over the needle seat represents the summary of all volumes between the needle seat to the discharge opening of the injector. The connection volume 5 represents the summary of all volumes which connects the storage chamber 3 and the control chamber 2 with the solenoid valve.

[0049] FIG. 4 shows an alternatively designed injector which does not require control chamber 2, e.g. an injector in which the needle 6 is controlled by a piezoelectric element.

[0050] The following equation system does not relate to the embodiment shown in FIG. 4. The formulation of a corresponding equation system can be performed analogously to the equation system shown below.

[0051] The dynamic behavior of the structural model is described by the following equation systems:

[0052] Pressure Dynamics

[0053] The evolution over time of the pressure within each of the volumes is calculated based on a combination of the mass conservation rate and the pressure-density characteristic of the liquid fuel. The evolution over time of the pressure results from:

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

[0054] Formula Symbols Used

p.sub.IA: Pressure in the input storage chamber 1 in bar
p.sub.CC: Pressure in the control chamber 2 in bar
p.sub.JC: Pressure in the connection volume 5 in bar
p.sub.AC: Pressure in the storage chamber 3 in bar
p.sub.SA: Pressure in the small storage chamber 4 in bar
p.sub.IA: Diesel mass density within the input storage chamber 1 in kg/m.sup.3
p.sub.CC: Diesel mass density within the control chamber 2 in kg/m.sup.3
p.sub.JC: Diesel mass density within the connection volume 5 in kg/m.sup.3
p.sub.AC: Diesel mass density within the storage chamber 3 in kg/m.sup.3
p.sub.SA: Diesel mass density within the small storage chamber 4 in kg/m.sup.3
K.sub.f: Bulk modulus of diesel fuel in bar

[0055] Needle Dynamics

[0056] The needle position is calculated by the following equation of motion:

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

[0057] Formula Symbols Used:

Z: Needle position in meters (m)
Z.sub.mas: Maximum deflection of the needle 6 in m
K: Spring stiffness in N/m
B: Spring damping coefficient in N.Math.s/m
F.sub.pre: Spring pretensioning in N
A.sub.AC: Hydraulic effective area in the storage chamber 3 in m.sup.2
A.sub.SA: Hydraulic effective area in the small storage chamber 4 in m.sup.2
A.sub.CC: Hydraulic effective area in the control chamber 2 in m.sup.2

[0058] Dynamics of the Solenoid Valve

[0059] The solenoid valve is modeled by a first order transfer function, which converts the valve opening command in a valve position. This is given by:

[0060] The transient system behavior is characterized by the time constant sol and the position of the needle 6 at the maximum valve opening is given by zmax sol. Instead of a solenoid valve, piezoelectric actuation is also possible.

[0061] Mass Flow Rates

[0062] The mass flow rate through each valve is calculated from the standard throttle equation for liquids, which is:

[00003]$\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{CR}}-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_{.Math.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{IA}}-p_{.Math.A.Math..Math.C}\right)& \mathrm{Eq}..Math.3.5\\ {\stackrel{.}{m}}_{\mathrm{aci}}=A_{\mathrm{aci}}.Math.C_{\mathrm{daci}}.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{ann}}.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.Math.}{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}$

[0063] Formula Symbols Used: [0064] {dot over (m)}.sub.in: Mass flow density through the input throttle in kg/s [0065] {dot over (m)}.sub.bd: Mass flow rate through the bypass valve between storage chamber 3 and the connection volume 5 in kg/s [0066] {dot over (m)}.sub.zd: Mass flow rate through the feed valve at the inlet of control chamber 2 in kg/s [0067] {dot over (m)}.sub.ad Mass flow rate through the outlet valve of control chamber 2 in kg/s [0068] {dot over (m)}.sub.sol: Mass flow rate through the solenoid valve in kg/s
{dot over (m)}.sub.aci: Mass flow rate through the inlet of storage chamber 3 in kg/s
{dot over (m)}.sub.ann: Mass flow rate through the needle seat in kg/s
{dot over (m)}.sub.inj: Mass flow rate through the injector nozzle in kg/s

[0069] Based on the above formulated injector model, the person skilled in the art obtains by means of the observer in a known manner (see, for example, Isermann, Rolf, 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) the estimated value {circumflex over (m)}.sub.d.

[0070] Using the above-mentioned equation systems, the so-called observer equations are constructed, using a known per se observer of the sliding mode observer type, by adding the so-called observer law to the equations of the injector model. In a sliding mode observer, the observer law is obtained by calculating a hypersurface from the at least one measuring signal and the value resulting from the observer equations. By squaring the hypersurface equation, we obtain a generalized Ljapunov equation (generalized energy equation). This is a functional equation. The observer law is the function that minimizes the functional equation. This can be determined by the variation techniques known per se or numerically. This process is carried out within one combustion cycle for each time step (depending on the time resolution of the control).

[0071] The result, depending on the application, is the estimated injected amount of liquid fuel, the position of the needle 6 or one of the pressures in one of the volumes of the injector.

[0072] This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention 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 languages of the claims.