Internal combustion engine

Abstract

An internal combustion engine is provided. The internal combustion engine includes a control device, and at least one injector for liquid fuel that includes a discharge opening for the liquid fuel. The at least one injector is connected to a collection volume by means of a line for liquid fuel. Liquid fuel can flow through the line for liquid fuel from the at least one injector to the collection volume. A control element that can be adjusted by the control device via a control signal is also provided. Via the control element, a back pressure in the line for liquid fuel can be adjusted in order to adjust an amount of liquid fuel discharged through the discharge opening of the at least one injector. Also provided is a method for operating an internal combustion engine and an injector.

Claims

1. An internal combustion engine comprising: a control device; and at least on injector for liquid fuel comprising a discharge opening for the liquid fuel; wherein the at least one injector is connected to a collection volume via a line for liquid fuel through which the liquid fuel can flow from the at least one injector to the collection volume; and wherein a control element, adjustable by the control device via a control signal, adjusts a back pressure in the line for liquid fuel to adjust an amount of liquid fuel discharged via the discharge opening of the at least one injector, at least in part by draining or leaking a separate amount of liquid fuel from the at least one injector, through the line for liquid fuel, and to the collection volume.

2. The internal combustion engine according to claim 1, wherein the control device controls or regulates the at least one injector using an actuator control signal, wherein a sensor is operable to measure a measurement variable of the at least one injector, wherein the sensor has a signal connection to the control device, and an algorithm is stored in the control device, which: receives as input variables at least the control signal for the control element, the actuator control signal, and/or measurement values corresponding to the measurement variable measured by the sensor; and using an injector model, calculates the amount of liquid fuel discharged via the discharge opening of the at least one injector, compares the amount of liquid fuel calculated via the injector model with a desired target value of the amount of liquid fuel, and causes the control device to adjust the back pressure in accordance with the result of the comparison.

3. The internal combustion engine according to claim 2, 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 control element to adjust the back pressure and/or the pilot control signal for the actuator control signal for the injection duration.

4. The internal combustion engine according to claim 3, wherein the algorithm comprises a feedback loop with: the pilot control signal calculated by the pilot control for the control element to adjust the back pressure and/or the actuator control signal calculated for an injection duration; and the measurement variable; and wherein the algorithm uses the feedback loop and the injector model to calculate the amount of liquid fuel discharged via the discharge opening of the at least one injector and, if necessary, corrects the pilot control signal calculated by the pilot control for the control element.

5. The internal combustion engine according to claim 2, wherein the algorithm comprises an observer which, via the injector model, uses the control signal for the control element and/or the actuator control signal, and the measurement variable, to estimate the amount of liquid fuel discharged via the discharge opening of the at least one injector.

6. The internal combustion engine according to claim 1, wherein the control element is designed as a control valve.

7. The internal combustion engine according to claim 1, wherein the at least one 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 a needle seat connected to the storage chamber; a connection volume connected on one side to the storage chamber and on the other side with the line for liquid fuel; the discharge opening for liquid fuel, which can be closed by a needle and is connected to the volume over the needle seat; and an actuator for the at least one injector 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.

8. The internal combustion engine according to claim 2, wherein the 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 at least one injector; pressure in a control chamber of the at least one injector; and start of a needle lift-off from a needle seat.

9. The internal combustion engine according to claim 2, 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 control signal for the control element in a subsequent combustion cycles.

10. The internal combustion engine according to claim 2, 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 deviations that have occurred and to make a correction of the control signal for the control element for a current or subsequent combustion cycle in accordance with the static evaluation.

11. The internal combustion engine according to claim 2, wherein the algorithm, using the injector model, causes the control device to adjust the actuator control signal in accordance with the result of the comparison.

12. An internal combustion engine comprising: a control device; and at least on injector for liquid fuel comprising a discharge opening for the liquid fuel; wherein the at least one injector is connected to a collection volume via a line for liquid fuel through which the liquid fuel can flow from the at least one injector to the collection volume; wherein a control element adjustable by the control device via a control signal, adjusts a back pressure in the line for liquid fuel to adjust an amount of liquid fuel discharged via the discharge opening of the at least one injector; wherein the control device controls or regulates the at least one injector using an actuator control signal, wherein a sensor is operable to measure a measurement variable of the at least one injector, wherein the sensor has a signal connection to the control device, and an algorithm is stored in the control device, which: receives as input variables at least the control signal for the control element, the actuator control signal, and/or measurement values corresponding to the measurement variable measured by the sensor; and using an injector model, calculates the amount of liquid fuel discharged via the discharge opening of the at least one injector, compares the amount of liquid fuel calculated via the injector model with a desired target value of the amount of liquid fuel, and causes the control device to adjust the back pressure in accordance with the result of the comparison; and wherein the injector model comprises at least: pressure progressions in volumes of the at least one injector at least partially filled with the liquid fuel; mass flow rates between the collection volume and at least one additional volume of the at least one injector at least partially filled with the liquid fuel; a position of a needle of the at least one injector relative to a needle seat corresponding to the needle; and solenoid valve dynamics of an actuator of the needle.

13. The internal combustion engine of claim 12, wherein the algorithm, using the injector model, causes the control device to adjust the actuator control signal in accordance with the result of the comparison.

14. An internal combustion engine comprising: a control device; and at least on injector for liquid fuel comprising a discharge opening for the liquid fuel; wherein the at least one injector is connected to a collection volume via a line for liquid fuel through which the liquid fuel can flow from the at least one injector to the collection volume; wherein a control element adjustable by the control device via a control signal, adjusts a back pressure in the line for liquid fuel to adjust an amount of liquid fuel discharged via the discharge opening of the at least one injector; wherein the control device controls or regulates the at least one injector using an actuator control signal, wherein a sensor is operable to measure a measurement variable of the at least one injector, wherein the sensor has a signal connection to the control device, and an algorithm is stored in the control device, which: receives as input variables at least the control signal for the control element, the actuator control signal, and/or measurement values corresponding to the measurement variable measured by the sensor; and using an injector model, calculates the amount of liquid fuel discharged via the discharge opening of the at least one injector, compares the amount of liquid fuel calculated via the injector model with a desired target value of the amount of liquid fuel, and causes the control device to adjust the back pressure in accordance with the result of the comparison; and 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 and/or a pilot control signal during this combustion cycle.

15. The internal combustion engine of claim 14, wherein the algorithm, using the injector model, causes the control device to adjust the actuator control signal in accordance with the result of the comparison.

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 an exemplary embodiment of a control diagram according to the disclosure; and

(3) FIG. 2 an example of a schematic representation of an injector.

DETAILED DESCRIPTION

(4) FIG. 1: 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 and/or the back pressure p (which is present in the line which connects the injector to a collection volume for liquid fuel). The control strategy is carried out by

(5) a pilot control (FF), which calculates from a desired target value of the amount m.sub.d.sup.ref of 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/or a pilot control signal for the control element and a feedback loop (FB) which, using an observer 7 (estimator) taking into account the control signal t calculated by the pilot control for the injection duration and/or the control signal for the control element 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 via the discharge opening of the injector estimated by means of the injector model and, if necessary, corrects the target value t.sub.ff calculated by the pilot control for the injection duration or the back pressure .sub.ff by means of correction factors t.sub.fb or .sub.fb (both of which can be negative).

(6) The pilot control ensures a fast system response by means of the actuator control signal, since it controls the injector with an injection duration t as if no injector variability would exist.

(7) 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 into the pilot control command t.sub.ff for the injection duration.

(8) 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 for the injection duration t and/or the back pressure p with the estimated injected amount of liquid fuel {circumflex over (m)}.sub.d and gives as feedback a correction control command for the injection duration t.sub.fb and/or the back pressure .sub.fb, 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 or .sub.ff. and .sub.fb gives the final injection duration t or the final back pressure p.

(9) The observer estimates the injected amount {circumflex over (m)}.sub.d of liquid fuel in dependence of the at least one measurement variable y and the final injection duration t and/or the final back pressure p. 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 start of the needle lift-off from the needle seat. The observer uses a reduced injector model to estimate the injected amount of liquid fuel.

(10) FIG. 2 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.

(11) 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.

(12) 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.

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

(14) Pressure Dynamics

(15) 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:

(16) $[{\stackrel{.}{p}}_{\mathrm{IA}}=\frac{K_f}{{}_{\mathrm{IA}}{V}_{\mathrm{IA}}}\left({\stackrel{.}{m}}_{\mathrm{in}}-{\stackrel{.}{m}}_{\mathrm{aci}}\right)[{\stackrel{.}{p}}_{\mathrm{CC}}=\frac{K_f}{{}_{\mathrm{CC}}{V}_{\mathrm{CC}}}\left({\stackrel{.}{m}}_{\mathrm{zd}}-{\stackrel{.}{m}}_{\mathrm{ad}}-{}_{\mathrm{CC}}{\stackrel{.}{V}}_{\mathrm{CC}}\right)[{\stackrel{.}{p}}_{\mathrm{JC}}=\frac{K_f}{{}_{\mathrm{JC}}{V}_{\mathrm{JC}}}\left({\stackrel{.}{m}}_{\mathrm{bd}}+{\stackrel{.}{m}}_{\mathrm{ad}}-{\stackrel{.}{m}}_{\mathrm{sol}}\right)[{\stackrel{.}{p}}_{\mathrm{AC}}=\frac{K_f}{{}_{\mathrm{AC}}{V}_{\mathrm{AC}}}\left({\stackrel{.}{m}}_{\mathrm{aci}}-{\stackrel{.}{m}}_{\mathrm{ann}}-{\stackrel{.}{m}}_{\mathrm{bd}}-{\stackrel{.}{m}}_{\mathrm{zd}}-{}_{\mathrm{AC}}{\stackrel{.}{V}}_{\mathrm{AC}}\right)[{\stackrel{.}{p}}_{\mathrm{SA}}=\frac{K_f}{{}_{\mathrm{SA}}{V}_{\mathrm{SA}}}\left({\stackrel{.}{m}}_{\mathrm{ann}}-{\stackrel{.}{m}}_{\mathrm{inj}}-{}_{\mathrm{SA}}{\stackrel{.}{V}}_{\mathrm{SA}}\right)$

(17) Formula Symbols Used

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

(19) p.sub.CC: Pressure in the control chamber 2 in bar

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

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

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

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

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

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

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

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

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

(29) Needle Dynamics

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

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

(32) Formula Symbols Used:

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

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

(35) K: Spring stiffness in N/m

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

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

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

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

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

(41) Dynamics of the Solenoid Valve

(42) 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:

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

(44) The transient system behavior is characterized by the time constant .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.

(45) Mass Flow Rates

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

(47) ${\stackrel{.}{m}}_{\mathrm{in}}=A_{\mathrm{in}}{C}_{\mathrm{din}}\sqrt{2{}_j\left|p_{\mathrm{CR}}-p_{\mathrm{IA}}\right|}.\mathrm{sgn}\left(p_{\mathrm{CR}}-p_{\mathrm{IA}}\right)]{\stackrel{.}{m}}_{\mathrm{bd}}=A_{\mathrm{bd}}{C}_{\mathrm{dbd}}\sqrt{2{}_j\left|p_{\mathrm{AC}}-p_{\mathrm{JC}}\right|}.\mathrm{sgn}\left(p_{\mathrm{AC}}-p_{\mathrm{JC}}\right)]{\stackrel{.}{m}}_{\mathrm{zd}}=A_{\mathrm{zd}}{C}_{\mathrm{dzd}}\sqrt{2{}_j\left|p_{\mathrm{AC}}-p_{\mathrm{CC}}\right|}.\mathrm{sgn}\left(p_{\mathrm{AC}}-p_{\mathrm{CC}}\right)]{\stackrel{.}{m}}_{\mathrm{ad}}=A_{\mathrm{od}}{C}_{\mathrm{dod}}\sqrt{2{}_j\left|p_{\mathrm{CC}}-p_{\mathrm{JC}}\right|}.\mathrm{sgn}\left(p_{\mathrm{CC}}-p_{\mathrm{JC}}\right)]{\stackrel{.}{m}}_{\mathrm{sol}}=A_{\mathrm{sol}}{C}_{\mathrm{dsol}}\sqrt{2{}_j\left|p_{\mathrm{JC}}-p_{\mathrm{LP}}\right|}.\mathrm{sgn}\left(p_{\mathrm{JC}}-p_{\mathrm{LP}}\right)]{\stackrel{.}{m}}_{\mathrm{aci}}=A_{\mathrm{aci}}{C}_{\mathrm{daci}}\sqrt{2{}_j\left|p_{\mathrm{IA}}-p_{\mathrm{AC}}\right|}.\mathrm{sgn}\left(p_{\mathrm{IA}}-p_{\mathrm{AC}}\right)]{\stackrel{.}{m}}_{\mathrm{ann}}=A_{\mathrm{ann}}{C}_{\mathrm{dann}}\sqrt{2{}_j\left|p_{\mathrm{AC}}-p_{\mathrm{SA}}\right|}.\mathrm{sgn}\left(p_{\mathrm{AC}}-p_{\mathrm{SA}}\right)]{\stackrel{.}{m}}_{\mathrm{inj}}=A_{\mathrm{inj}}{C}_{\mathrm{dinj}}\sqrt{2{}_{\mathrm{SA}}\left|p_{\mathrm{SA}}-p_{\mathrm{cyl}}\right|}.\mathrm{sgn}\left(p_{\mathrm{SA}}-p_{\mathrm{cyl}}\right)]{}_j=\{\begin{array}{c}{}_{\mathrm{in}}\mathrm{if}{p}_{\mathrm{in}}{p}_{\mathrm{out}}\\ {}_{\mathrm{out}}\mathrm{if}{p}_{\mathrm{in}}>p_{\mathrm{out}}\end{array}$

(48) Formula Symbols Used:

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

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

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

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

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

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

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

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

(57) 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.

(58) 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 given by the following 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).

(59) 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.

(60) 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.