Internal combustion engine with injection quantity control

Abstract

An internal combustion engine is provided. The internal combustion engine includes a control device, and at least one injector for liquid fuel. The injector(s) can be controlled by the control device via an actuator control signal. The injector(s) include an injector outlet opening for the liquid fuel which can be closed by a needle. A sensor is also provided for measuring a measurement variable of the injector(s). The sensor is or can be in a signal connection with the control device. An algorithm is stored in the control device, which algorithm calculates a state of the injector(s) based on input variables and an injector model, compares the state calculated via the injector model with a target state, and produces a state signal in accordance therewith. The state signal is characteristic of a change in the state of the injector(s) that occurs during intended use of the injector(s) and/or an unforeseen change in the state of the injector(s). The input variables include at least the actuator control signal and the measurement values of the sensor. A method for operating such an internal combustion engine and an injector is also provided.

Claims

1. An internal combustion engine, comprising: a control device; at least one injector for liquid fuel, configured to be controlled by the control device via an actuator control signal, wherein the at least one injector comprises an injector outlet opening for the liquid fuel which is closed by a needle; and a sensor, by which a measurement variable of the at least one injector can be measured, wherein the sensor is configured to communicate with the control device, wherein the control device is configured to: calculate a state of the injector on the basis of input variables that comprise at least the actuator control signal and the measurement values of the sensor, and an injector model, compare the state with a target state, produce a state signal, wherein the state signal is representative of a change in the state of the injector that occurs during use of the injector, an unforeseen change in the state of the injector, or a combination thereof, wherein the injector model comprises; pressure progressions in the volumes of the injector filled with the liquid fuel; mass flow rates between the volumes of the injector filled with the liquid fuel; a kinematic variable of the needle being a position of the needle relative to the needle seat; and dynamics of the actuator of the needle.

2. The internal combustion engine of claim 1, wherein the control device is configured to provide a pilot control to derive a pilot control signal based on a desired target value of a mass of the liquid fuel, a needle position target value, or a combination thereof, and wherein the pilot control signal is used to control the at least one injector during a pilot mode of operations of the internal combustion engine.

3. The internal combustion engine of claim 2, wherein the control device is configured to provide a feedback loop that uses the pilot control signal calculated by the pilot control and the at least one measurement variable to calculate an output mass of the liquid fuel through an injector outlet opening, the position of the needle, or a combination thereof, and corrects the actuator control signal based on the output mass of the liquid fuel.

4. The internal combustion engine of claim 1, wherein the control device executes an observer, which, using the injector model, the actuator control signal and the at least one measurement variable as inputs, estimates an injected mass of liquid fuel and or the position of the needle to calculate the output mass of the liquid fuel.

5. The internal combustion engine of claim 1, wherein the dynamics of the actuator of the needle comprise solenoid valve dynamics.

6. The internal combustion engine of claim 1, wherein the injector comprises at least: an input storage chamber connected to a common rail of the internal combustion engine; a storage chamber for liquid fuel connected to the input storage chamber; a volume over the needle seat connected to the storage chamber; a connection volume connected on one side to the storage chamber and on the other side to a drain line; an outlet opening for liquid fuel, which can be closed by a 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; and a control chamber connected on one side to the storage chamber and on the other side to the connection volume.

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

8. The internal combustion engine of claim 7, wherein the control device is configured to produce a state signal which provides information about a deviation of at least one of the measurement variables relative to a predetermined value.

9. The internal combustion engine of claim 1, wherein the control device is configured to calculate the state and produce the state signal during each combustion cycle of the internal combustion engine.

10. The internal combustion engine of claim 1, wherein the control device is configured to calculate the state and produce the state signal during selected combustion cycles of the internal combustion engine.

11. The internal combustion engine of claim 1, wherein the control device is configured to calculate the state and produce the state signal during each combustion cycle or selected combustion cycles of the internal combustion engine and to statically evaluate the deviations that have occurred.

12. The internal combustion engine of claim 1, wherein the control device is configured to determine on the basis of the state signal a remaining service life of the injector, whether the injector is to be replaced, or a combination thereof.

13. The internal combustion engine of claim 1, wherein the control device is configured to, based on the state signal, a correction of the actuator control signal, the pilot control signal, or a combination thereof.

14. A method for operating an internal combustion engine, comprising: supplying a combustion chamber of the internal combustion engine with liquid fuel; sensing at least one measurement variable from an injector for injecting liquid fuel and disposed in the internal combustion engine; calculating based on input variables and an injector model, a state of the injector; comparing the state of the injector with a target state; and depending on the result; and producing a state signal characteristic of a change in the state of the injector that occurs during an intended use of the injector, an unforeseen change in the state of the injector, or a combination thereof; wherein the input variables comprise at least the actuator control signal and the measurement values of the sensor, wherein the injector model comprises; pressure progressions in the volumes of the injector filled with the liquid fuel; mass flow rates between the volumes of the injector filled with the liquid fuel; a kinematic variable of a needle of the injector comprising a position of the needle relative to a needle seat; and dynamics of an actuator of the needle.

15. The method of claim 14, wherein the dynamics of the actuator of the needle comprise solenoid valve dynamics.

16. The method of claim 14, wherein the at least one measurement variable is selected from the following variables or a combination thereof: pressure in a common rail of the internal combustion engine; pressure in an input storage chamber of the injector; pressure in a control chamber of the injector; and start of a needle lift-off from a needle seat of the injector.

17. The method of claim 14, wherein producing the state signal comprises producing the state signal during each combustion cycle of the internal combustion engine.

18. The method of claim 14, wherein producing the state signal comprises producing the state signal during selective combustion cycles of the internal combustion engine.

19. A controller of an internal combustion engine, the controller configured to: supply a combustion chamber of the internal combustion engine with liquid fuel; sense at least one measurement variable from an injector for injecting liquid fuel and disposed in the internal combustion engine; calculate based on input variables and an injector model, a state of the injector; compare the state of the injector with a target state; and depending on the result; and produce a state signal characteristic of a change in the state of the injector that occurs during an intended use of the injector, an unforeseen change in the state of the injector, or a combination thereof; wherein the input variables comprise at least the actuator control signal and the measurement values of the sensor, wherein the injector model comprises; pressure progressions in the volumes of the injector filled with the liquid fuel; mass flow rates between the volumes of the injector filled with the liquid fuel; a kinematic variable of a needle of the injector comprising a position of the needle relative to a needle seat; and dynamics of an actuator of the needle.

20. The controller of claim 19, wherein the dynamics of the actuator of the needle comprises solenoid valve dynamics.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the disclosure are explained in more detail by the figures below. They are as follows:

(2) FIG. 1 a first exemplary embodiment of a first control diagram

(3) FIG. 2 a second exemplary embodiment of a second control diagram

(4) FIG. 3 a first example of a schematic representation of an injector

(5) FIG. 4 a second example of a schematic representation of an injector

DETAILED DESCRIPTION

(6) FIG. 1:

(7) The object of the injector control in this exemplary embodiment is the control of the actual injected amount of liquid fuel and/or the position z of the needle to a target value m.sub.d.sup.ref or z.sup.ref, by controlling the injection duration or the duration of actuation of the actuator of the needle Δt. The control strategy is carried out by a pilot control (FF), which consist of a desired target value of the amount m.sub.d.sup.ref on liquid fuel and/or a needle position target value z.sup.ref calculates a pilot control signal Δt.sub.ff (hereinafter also referred to as “control command”) for the injection duration or the duration of actuation of the actuator and a feedback loop (FB) which, using an observer 7 (“state estimator”), taking into account the pilot control signal Δt.sub.ff calculated by the pilot control 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 needle lift-off from the needle seat), the mass flow {circumflex over (m)}.sub.d of liquid fuel discharged via the discharge opening of the injector and/or the position of the needle {circumflex over (z)} estimated by means of the injector model and, if necessary, corrects the pilot control signal Δt.sub.ff calculated by the pilot control by means of a correction value Δt.sub.fb. The observer also outputs the state signal C.

(8) The pilot control ensures a fast system response, since it controls the injector with an injection duration Δt as if no injector variability would exist. The pilot control uses a calibrated injector map (which indicates the duration of current flow over the injection amount or volume) or an inverted injector model to convert the target value of the amount m.sub.d.sup.ref of liquid fuel and/or the needle position target value z.sup.ref into the pilot control command Δt.sub.ff.

(9) 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 and/or z.sup.ref with the estimated injected amount {circumflex over (m)}.sub.d of liquid fuel or the estimated position of the needle {circumflex over (z)} and gives as feedback a correction control command Δt.sub.fb (which can also be negative) for the injection duration or the duration of actuation of the actuator, if there is a discrepancy between m.sub.d.sup.ref and {circumflex over (m)}.sub.d or z.sup.ref and {circumflex over (z)}. The addition of Δt.sub.ff and Δt.sub.fb gives the final injection duration Δt or the duration of actuation of the actuator.

(10) The observer estimates the injected amount {circumflex over (m)}.sub.d of liquid fuel and/or the position of the needle {circumflex over (z)} in dependence of the at least one measurement variable y and the final injection duration Δt or the duration of actuation of the actuator. The at least one measurement variable 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 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 or the position of the needle {circumflex over (z)}.

(11) FIG. 2

(12) This figure shows a one-piece control, in which the actuator control signal Δt is calculated based on the target value m.sub.d.sup.ref for the injected amount of liquid fuel and/or the needle position target value z.sup.ref and based on the parameter Δpar.sub.mod used in the pilot control model and estimated by the observer. This gives an adaptive pilot control signal modified by the observer. In this case, the control is therefore not constructed in two parts, with a pilot control and a feedback loop correcting the pilot control signal.

(13) FIG. 3

(14) 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 4 and connection volume 5.

(15) The input storage chamber 1 represents the summary of all volumes between the input choke and the non-return valve. The storage chamber 3 represents the summary of all volumes from the non-return valve to volume 4 above the needle seat. The volume 4 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.

(16) 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 piezo element.

(17) The following equation system is not related to the embodiment shown in FIG. 4. The formulation of a corresponding equation system may be analogous to that shown below.

(18) The dynamic behavior of the structure model is described by the following equation systems:

(19) Pressure Dynamics

(20) The temporal evolution of the pressure within each of the volumes is calculated based on a combination of the mass conservation law and the pressure density characteristic of the liquid fuel. The temporal evolution of the pressure follows from:

(21) $\begin{array}{cc}{\stackrel{.}{p}}_{\mathrm{IA}}=\frac{K_f}{{\rho }_{\mathrm{IA}}{V}_{\mathrm{IA}}}\left({\stackrel{.}{m}}_{\mathrm{in}}-{\stackrel{.}{m}}_{\mathrm{aci}}\right)& \mathrm{Eq}.1.1\\ {\stackrel{.}{p}}_{\mathrm{CC}}=\frac{K_f}{{\rho }_{\mathrm{CC}}{V}_{\mathrm{CC}}}\left({\stackrel{.}{m}}_{\mathrm{zd}}-{\stackrel{.}{m}}_{\mathrm{ad}}-{\rho }_{\mathrm{CC}}{\stackrel{.}{V}}_{\mathrm{CC}}\right)& \mathrm{Eq}.1.2\\ {\stackrel{.}{p}}_{\mathrm{JC}}=\frac{K_f}{{\rho }_{\mathrm{JC}}{V}_{\mathrm{JC}}}\left({\stackrel{.}{m}}_{\mathrm{bd}}+{\stackrel{.}{m}}_{\mathrm{ad}}+{\stackrel{.}{m}}_{\mathrm{sol}}\right)& \mathrm{Eq}.1.3\\ {\stackrel{.}{p}}_{\mathrm{AC}}=\frac{K_f}{{\rho }_{\mathrm{AC}}{V}_{\mathrm{AC}}}\left({\stackrel{.}{m}}_{\mathrm{aci}}-{\stackrel{.}{m}}_{\mathrm{ann}}-{\stackrel{.}{m}}_{\mathrm{bd}}-{\stackrel{.}{m}}_{\mathrm{zd}}-{\rho }_{\mathrm{AC}}{\stackrel{.}{V}}_{\mathrm{AC}}\right)& \mathrm{Eq}.1.4\\ {\stackrel{.}{p}}_{\mathrm{SA}}=\frac{K_f}{{\rho }_{\mathrm{SA}}{V}_{\mathrm{SA}}}\left({\stackrel{.}{m}}_{\mathrm{ann}}-{\stackrel{.}{m}}_{\mathrm{inj}}-{\rho }_{\mathrm{SA}}{\stackrel{.}{V}}_{\mathrm{SA}}\right)& \mathrm{Eq}.1.5\end{array}$

(22) Formula Symbols Used

(23) p.sub.IA: Pressure in the input storage chamber 1 in bar

(24) p.sub.cc: Pressure in the control chamber 2 in bar

(25) p.sub.JC: Pressure in the connection volume 5 in bar

(26) p.sub.AC: Pressure in the storage chamber 3 in bar

(27) p.sub.SA: Pressure in the small storage chamber 4 in bar

(28) p.sub.IA: Diesel mass density within the input storage chamber 1 in kg/m.sup.3

(29) p.sub.CC: Diesel mass density within the control chamber 2 in kg/m.sup.3

(30) p.sub.JC: Diesel mass density within the connection volume 5 in kg/m.sup.3

(31) p.sub.AC: Diesel mass density within the storage chamber 3 in kg/m.sup.3

(32) p.sub.SA: Diesel mass density within the small storage chamber 4 in kg/m.sup.3

(33) K.sub.f: Bulk modulus of diesel fuel in bar

(34) Needle Dynamics

(35) The needle position is calculated by the following equation of motion:

(36) $[\stackrel{\mathrm{.Math.}}{z}=\{\begin{array}{cc}0& \mathrm{if}{F}_{\mathrm{hyd}}\le F_{\mathrm{pre}}\\ \frac{1}{m}\left(F_{\mathrm{hyd}}-\mathrm{Kz}-B\stackrel{.}{z}-F_{\mathrm{pre}}\right)& \mathrm{if}{F}_{\mathrm{hyd}}>F_{\mathrm{pre}}\end{array}[F_{\mathrm{hyd}}=p_{\mathrm{AC}}{A}_{\mathrm{AC}}+p_{\mathrm{SA}}{A}_{\mathrm{SA}}-p_{\mathrm{CC}}{A}_{\mathrm{CC}}[0\le z\le z_{\max }$

(37) Formula Symbols Used:

(38) Z: Needle position in meters (m)

(39) Z.sub.max: Maximum deflection of the needle 6 in m

(40) K: Spring stiffness in N/m

(41) B: Spring damping coefficient in N.s/m

(42) F.sub.pre: Spring preload in N

(43) A.sub.AC: Hydraulic effective area in the storage chamber 3 in m.sup.2

(44) A.sub.SA: Hydraulic effective area in the small storage chamber 4 in m.sup.2

(45) A.sub.CC: Hydraulic effective area in the control chamber 2 in m.sup.2

(46) Dynamics of the Solenoid Valve

(47) 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:

(48) $\begin{array}{cc}\stackrel{u_{\mathrm{sol}}^{\mathrm{cmd}}}{.fwdarw.}\frac{z_{\mathrm{sol}}^{\max }}{{\tau }_{\mathrm{sol}}s+1}\stackrel{z_{\mathrm{sol}}}{.fwdarw.}& \end{array}$

(49) The transient system behavior is characterized by the time constant τ.sub.sol and the position of the needle 6 at the maximum valve opening is given by z.sub.sol.sup.max. Instead of a solenoid valve, a piezoelectric actuation is possible.

(50) Mass Flow Rates

(51) The mass flow rate through each valve is calculated from the standard throttle equation for liquids, which is:

(52) $\begin{array}{cc}{\stackrel{.}{m}}_{\mathrm{in}}=A_{\mathrm{in}}{C}_{\mathrm{din}}\sqrt{2{\rho }_j.Math.p_{\mathrm{CR}}-p_{\mathrm{IA}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{CR}}-p_{\mathrm{IA}}\right)& \mathrm{Eq}.3.1\\ {\stackrel{.}{m}}_{\mathrm{bd}}=A_{\mathrm{bd}}{C}_{\mathrm{dbd}}\sqrt{2{\rho }_j.Math.p_{\mathrm{AC}}-p_{\mathrm{JC}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{AC}}-p_{\mathrm{JC}}\right)& \mathrm{Eq}.3.2\\ {\stackrel{.}{m}}_{\mathrm{zd}}=A_{\mathrm{zd}}{C}_{\mathrm{dzd}}\sqrt{2{\rho }_j.Math.p_{\mathrm{AC}}-p_{\mathrm{CC}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{AC}}-p_{\mathrm{CC}}\right)& \mathrm{Eq}.3.3\\ {\stackrel{.}{m}}_{\mathrm{ad}}=A_{\mathrm{ad}}{C}_{\mathrm{dad}}\sqrt{2{\rho }_j.Math.p_{\mathrm{CC}}-p_{\mathrm{JC}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{CC}}-p_{\mathrm{JC}}\right)& \mathrm{Eq}.3.4\\ {\stackrel{.}{m}}_{\mathrm{sol}}=A_{\mathrm{sol}}{C}_{\mathrm{dsol}}\sqrt{2{\rho }_j.Math.p_{\mathrm{JC}}-p_{\mathrm{LP}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{JC}}-p_{\mathrm{LP}}\right)& \mathrm{Eq}.3.5\\ {\stackrel{.}{m}}_{\mathrm{aci}}=A_{\mathrm{aci}}{C}_{\mathrm{daci}}\sqrt{2{\rho }_j.Math.p_{\mathrm{IA}}-p_{\mathrm{AC}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{IA}}-p_{\mathrm{AC}}\right)& \mathrm{Eq}.3.6\\ {\stackrel{.}{m}}_{\mathrm{ann}}=A_{\mathrm{ann}}{C}_{\mathrm{dann}}\sqrt{2{\rho }_j.Math.p_{\mathrm{AC}}-p_{\mathrm{SA}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{AC}}-p_{\mathrm{SA}}\right)& \mathrm{Eq}.3.7\\ {\stackrel{.}{m}}_{\mathrm{inj}}=A_{\mathrm{inj}}{C}_{\mathrm{dinj}}\sqrt{2{\rho }_{\mathrm{SA}}.Math.p_{\mathrm{SA}}-p_{\mathrm{cyl}}.Math.}.Math.\mathrm{sgn}\left(p_{\mathrm{SA}}-p_{\mathrm{cyl}}\right)& \mathrm{Eq}.3.8\\ p_j=\{\begin{array}{cc}{\rho }_{\mathrm{in}}& \mathrm{if}{p}_{\mathrm{in}}\ge p_{\mathrm{out}}\\ {\rho }_{\mathrm{out}}& \mathrm{if}{p}_{\mathrm{in}}<p_{\mathrm{out}}\end{array}& \mathrm{Eq}.3.9\end{array}$

(53) Formula Symbols Used:

(54) {dot over (m)}.sub.in: mass flow rate through each input choke in kg/s

(55) {dot over (m)}.sub.bd: mass flow rate through the bypass valve between storage chamber 3 and the connection volume 5 in kg/s

(56) {dot over (m)}.sub.zd: mass flow rate through the feed valve at the inlet of the control chamber 2 in kg/s

(57) {dot over (m)}.sub.ad: mass flow rate through the outlet valve of the control chamber 2 in kg/s

(58) {dot over (m)}.sub.sol: mass flow rate through the solenoid valve in kg/s

(59) {dot over (m)}.sub.aci: mass flow rate through the inlet of the storage chamber 3 in kg/s

(60) {dot over (m)}.sub.ann: mass flow rate through the needle seat in kg/s

(61) {dot over (m)}.sub.inj: mass flow rate through the injector nozzle in kg/s

(62) 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 SSSC—5th Symposium on System Structure and Control, Grenoble, France 2013) the estimated value {circumflex over (m)}.sub.d and/or {circumflex over (z)} and the state signal C.

(63) Using the above equation systems, the so-called “observer equations” are constructed, in an embodiment using a known observer of the “sliding mode observer” type, by adding the so-called “observer law” to the equations of the injector model. With 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 equation of the hypersurface, a generalized Ljapunov equation (generalized energy equation) is obtained. It is a functional equation. The observer law is that function which minimizes the functional equation. This can be determined by the known variation techniques or numerically. This process is carried out within one combustion cycle for each time step (depending on the time resolution of the control).

(64) The result is depending on the application, 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.