DE102019129323A1 - Method for volume flow-based, pump-synchronous and cylinder-selective rail pressure control for a fuel supply system of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for regulating a rail pressure (p7Soll) caused by a high pressure pump (1) in a fuel accumulator (4) for a fuel supply system (100) of an internal combustion engine, with a crank angle-related or cam angle-related fixed angle difference of the internal combustion engine between a top dead center position a cylinder piston of a cylinder of the internal combustion engine and a top dead center position of the pump piston of the high pressure pump (1) of the fuel supply system (100) is taken into account in the metering of the delivery volume of the high pressure pump (1). It is provided that recurring pumping synchronously per segment that one Rotation of a crankshaft and thus the movement of the pump piston of the high-pressure pump (1) from the top dead center position of the pump piston to the next top dead center position, a control deviation (Δp7) of the rail pressure (p7) in the fuel accumulator (4) is discretized and from the d A volume-related discrete cylinder-selective volume control difference (ΔVRail) is calculated based on the iscrete control deviation (Δp7)

Description

The invention relates to a method for regulating a rail pressure caused by a high pressure pump in a fuel accumulator for a fuel supply system of an internal combustion engine, wherein a crank angle-related or cam angle-related fixed angular difference of the internal combustion engine between an upper dead center position of a cylinder piston of a cylinder of the internal combustion engine and an upper dead center Position of the pump piston of the high-pressure pump of the fuel supply system is taken into account when metering the delivery volume of the high-pressure pump.

From the pamphlet DE 10 2016 204 386 A1 a method for regulating a rail pressure caused by a high pressure pump in a fuel rail for an internal combustion engine is already known, in which the rail pressure is regulated in synchronism with an engine speed of the internal combustion engine of the high pressure pump. The regulation of the rail pressure does not take place in the known fixed, time-synchronous calculation grid, but takes place in a time-variable, engine-speed-synchronous calculation grid, the respective grid interval of which is preferably from one top dead center to the next, based on a single cylinder or all cylinders of the internal combustion engine extends. The high-pressure pump provides an amount of fuel with each pump delivery stroke. The sequence of the pump delivery strokes of the high-pressure pump does not follow the fixed scanning pattern of the rail pressure regulator in terms of time, but is determined by the current operating state of the internal combustion engine.

The known fuel supply system comprises a rail pressure regulator for using the proposed method. A high-pressure pump is supplied with fuel from a tank by a pre-feed pump via a low-pressure line. The high-pressure pump pumps fuel into a fuel rail via a high-pressure line. The delivery volume of the high pressure pump is set according to a delivery volume control value that a rail pressure regulator has calculated to regulate the rail pressure in the fuel rail. The rail pressure controller is composed of a PID controller and a pilot control unit. A rail pressure control deviation is fed to the PID controller, which is calculated as the difference between the rail pressure setpoint value calculated synchronously with the engine speed and the actual rail pressure value recorded synchronously with the engine speed with a rail pressure sensor, and calculates an additive corrective volume flow synchronously with the engine speed. A calculation carried out synchronously with the engine speed means that this calculation is carried out once for each top dead center of the internal combustion engine that has passed through.

The pilot control unit is supplied with an injection quantity calculated synchronously with the engine speed and a desired pressure change value, so that the pilot control unit calculates a pilot control value synchronously with the engine speed. The sum of the additive correction volume flow and the precontrol value is fed to the high-pressure pump as a delivery volume control value in order to specify the delivery volume of the current delivery stroke and to set the rail pressure setpoint ps in the fuel rail.

The invention is based on the object of improving the rail pressure regulation.

The starting point of the invention is that with a classic time-synchronous rail pressure control that works in a 10 ms sampling grid, depending on the engine speed, the engine-synchronous pump event is under- or oversampling. This disadvantageously results in pressure fluctuations in the form of beats and aliasing, which cannot be fully regulated even at stationary operating points.

These effects have a particularly negative effect on modern high-pressure pumps, in which the delivery volume is influenced from one delivery stroke to the next (the next in the entire setting range). So far, only an extremely low loop gain provides a remedy, with the result that the classic time-synchronous rail pressure regulator, in particular in dynamic pressure change situations, is far inferior to the method according to the invention explained below.

The conventional rail pressure control should be adapted to the task of the newly available high pressure pumps, which can provide a volume flow for each work cycle.

The best possible control performance with deviations between setpoint and actual value of less than 2% of the current setpoint should be achieved. Furthermore, computing time and code memory in the control unit should be saved, the calibration and validation effort should be reduced and simple adaptation to different pump designs, pressure control valve variants and high-pressure components should be made possible.

According to the preceding statements, a method for regulating a rail pressure caused by a high-pressure pump in a fuel accumulator for a fuel supply system of an internal combustion engine is known, with a crank angle-related or cam angle-related fixed angular difference of the internal combustion engine between a top dead center position of a cylinder piston of a cylinder of the internal combustion engine and a top dead center position of the pump piston of the high pressure pump of the fuel supply system is taken into account in the metering of the delivery volume of the high pressure pump.

According to the invention it is now provided that recurring pump-synchronously per segment, which corresponds to one revolution of a crankshaft and thus the movement of the pump piston of the high-pressure pump from the top dead center position of the pump piston to the next top dead center position, a discretization of a control deviation of the rail pressure in the fuel accumulator and based on the discrete control deviation, a volume-related discrete volume control difference is calculated for each cylinder.

Preferably, the volume-related discrete volume control difference is fed as an input variable to a control module for the high-pressure pump and a control module for a pressure control valve assigned to the fuel accumulator, the discrete volume control difference being linked to a pilot control module, whereby the manipulated variables for each segment are synchronized with the pump and cylinder-specific The high-pressure pump and the pressure regulating valve are calculated in an output module and fed to the actuators of the high-pressure pump and the pressure regulating valve for the volume-based, cylinder-selective setting of the rail pressure.

Furthermore, the discrete control deviation is preferably calculated cylinder-selectively as the difference between the discretized actual rail pressure and the discretized target rail pressure by comparing discretized pressure information from a rail pressure sensor of the actively detected pump-synchronous segment with the discretized target rail pressure of the previous pump-synchronous segment by one work cycle to determine the discrete cylinder-selective control difference.

According to the invention, the target rail pressure is discretized at a point in time that is established with a trigger start signal that is output repeatedly at the beginning of a pump-synchronous segment. Provision is made for the actual rail pressure within the segment started by the trigger start signal to be repeatedly recorded and discretized.

• - in dem Segment maximaler Ist-Raildruck und
• - in dem Segment minimaler Ist-Raildruck und
• - in dem Segment berechneter Mittelwert

diskretisiert und wahlweise mit dem diskretisierten Soll-Raildruck zur Bestimmung der diskreten zylinderselektiven Regelabweichung verglichen wird.It is preferably provided that the actual rail pressure, which is recurring detected within the pump-synchronous segment, as

• - in the segment maximum actual rail pressure and
• - in the segment minimum actual rail pressure and
• - mean calculated in the segment

is discretized and optionally compared with the discretized target rail pressure to determine the discrete cylinder-selective control deviation.

It is also preferred that the recorded minimum discrete pressure or the recorded maximum discrete pressure or the discrete mean value for comparison with the discrete setpoint rail pressure is used as the actual value for the cylinder-selective control, with the maximum discrete pressure build-up depending on the system requirements Pressure and, in the event of a pressure reduction, the minimum discrete pressure is used to reduce control oscillations for each cylinder or to avoid overshoot or undershoot for each cylinder.

A special aspect of the invention also provides that the discrete cylinder-selective control deviation is converted into the volume flow-based discrete cylinder-selective volume control difference, with a permanent fuel leakage of the high-pressure system of the fuel supply system being additionally taken into account by addition.

zylinderselektiv berücksichtigt wird.The pressure-based discretized cylinder-selective control difference Δp _rail is advantageously converted into a volume flow-based, cylinder-selective volume control difference AV _Rail converted, with the pressure and temperature-dependent specific modulus of elasticity during the conversion E. of the respective fuel and the volume of space V _H of the high pressure fuel system of the fuel supply system according to the conversion formula $$\Delta {\text{V}}_{\text{Rail}}=\frac{V_{\text{H}}}{\mathrm{E.}\left(p,T\right)}\ast \Delta {\text{p}}_{\text{Rail}}$$

is considered cylinder-selective.

• a) zylinderselektiv die Kraftstoff-Einspritzmengen der Injektoren und
• b) zylinderselektiv die Kraftstoff-Schaltleckagen der Injektoren und
• d) zylinderselektiv ein Druckänderungswunsch bezüglich des Soll-Raildrucks des Kraftstoffspeichers berücksichtigt, wobei ferner
• c) die Kraftstoff-Dauerleckage des Hochdrucksystems des Kraftstoffversorgungssystems durch eine pumpensynchrone segmentweise wiederkehrende separate Umrechnung mit einer Z-Transformation ermittelt und der volumenbezogenen diskreten zylinderselektiven Volumen-Regeldifferenz hinzugefügt wird.

In the case of the pump-synchronous, segment-wise recurring conversion of the pressure-based discrete cylinder-selective control deviation into the volume-related discrete volume-cylinder-selective control difference,

• a) the fuel injection quantities of the injectors and cylinder-selective
• b) the fuel switching leaks of the injectors and cylinder-selective
• d) a pressure change request with regard to the target rail pressure of the fuel accumulator is taken into account in a cylinder-selective manner, and furthermore
• c) the permanent fuel leakage of the high pressure system of the fuel supply system by a pump synchronous segment-wise recurring separate conversion is determined with a Z-transformation and added to the volume-related discrete cylinder-selective volume control difference.

According to the invention, it is provided that the injectors receive the same quantity target values from cylinder to cylinder in stationary operation, which are compared cylinder-selectively with the quantity decreases from the rail, with injection quantity errors being determined for each cylinder, which are assigned to the injectors, one type of quantity deviations being determined Is assigned to error groups. The injection quantity errors are advantageously grouped depending on the cause, in particular depending on the level of the injection quantity error resulting from the target / actual comparison, with the injectors being operated in a fault group with an injector defect, an error group with an age-related injector drift or an error group with a changing Switching leakage quantity are assigned, the injection quantity errors being determined within the cylinder-selective regulation in the controller and corrected in the injection system and / or leading to an exchange of the respective injector (s).

A correction in the injection system can be made in various ways. In a preferred embodiment, the correction takes place by changing the injector control duration.

• - einen Sollwertvorgabe-Baustein des Raildrucks und eine zugehörigen Sollwert-Diskretisierungs-Baustein und
• - einen Istwert-Signalerfassungs-Baustein des Raildruck und einen Istwert-Diskretisierungs-Baustein,
• - sowie einen Regelfehler-Berechnungs-Baustein und
• - einen Umrechnungs-Baustein umfasst, der aus einer druckbasierten diskretisieren zylinderselektiven Regeldifferenz eine Umrechnung in eine volumenstrombasierte zylinderselektive Regeldifferenz vornimmt,
• - wobei der Umrechnungs-Baustein mit einer Regler-Zustandsmaschine verknüpft ist, welche zylinderselektiv die diskrete Eingangsgröße dem jeweiligen Regler-Baustein der Hochdruckpumpe und zylinderselektiv die diskreten Eingangsgröße dem jeweiligen Regler-Baustein des Druckregelventils ausgibt,
• - wobei die Regler-Bausteine jeweils zylinderselektiv mit einem Vorsteuer-Baustein verknüpft sind, wodurch mittels des Vorsteuer-Bausteins und der aufgeschalteten zylinderselektiven Regler-Bausteine pumpensynchron je Segment die Stellgrößen für die Hochdruckpumpe und das Druckregelventil einem Ausgabe-Baustein zugeführt und berechnet werden, und den Stellgliedern der Hochdruckpumpe und des Druckregelventils zur volumenbasierten zylinderselektiven Einstellung des Raildrucks zugeführt werden.

The fuel supply system associated with the method is set up to carry out the method, with the fuel supply system cylinder-selective multiple controller modules for the high-pressure pump to determine the respective discrete input variable of the respective cylinder and several cylinder-selective controller modules for a dem to determine a discrete input variable of the respective cylinder Fuel accumulator associated pressure control valve includes the following additional modules,

• - A setpoint specification module for the rail pressure and an associated setpoint discretization module and
• - an actual value signal acquisition module for the rail pressure and an actual value discretization module,
• - as well as a control error calculation module and
• - includes a conversion module that converts a pressure-based, discretized, cylinder-selective control difference into a volume flow-based, cylinder-selective control difference,
• - The conversion module being linked to a controller state machine which outputs the discrete input variable to the respective controller module of the high-pressure pump on a cylinder-specific basis and the discrete input variable to the respective controller module of the pressure control valve on a cylinder-specific basis,
• - The controller modules are each cylinder-selectively linked with a pilot control module, whereby by means of the pilot control module and the connected cylinder-selective controller modules pump-synchronously per segment, the manipulated variables for the high pressure pump and the pressure control valve are fed to an output module and calculated, and the actuators of the high pressure pump and the pressure control valve for volume-based cylinder-selective adjustment of the rail pressure.

The internal combustion engine is advantageously operated with any liquid fuel or fuel mixture, as a result of which the linearization of the conversion of pressure difference into volume flow difference can be adapted to the respective fuel by a physically different modulus of elasticity. As a result, the explained method and the configuration of the fuel supply system can be used and used not only for diesel engines that are designed in particular as common rail diesel engines, but also for Otto engines that use an Otto engine - externally ignited - combustion process.

• 1 eine schematische Darstellung eines Kraftstoffversorgungssystems, das mit einer volumenstrombasierten pumpensynchronen und zylinderselektiven Regelstruktur zur Raildruckregelung gemäß dem erfindungsgemäßen Verfahren betrieben wird;
• 2 die volumenstrombasierte pumpensynchrone und zylinderselektiven Regelstruktur zur Raildruckregelung, die in einem elektronischen Steuergerät mit einem Mikroprozessor abgelegt ist, das zur Ausführung des erfindungsgemäßen Verfahrens eingerichtet ist.

The invention is explained below with reference to the accompanying drawings. Show it:

• 1 a schematic representation of a fuel supply system that is operated with a volume flow-based pump-synchronous and cylinder-selective control structure for rail pressure control according to the method according to the invention;
• 2 the volume flow-based pump-synchronous and cylinder-selective control structure for rail pressure control, which is stored in an electronic control unit with a microprocessor which is set up to carry out the method according to the invention.

The 1 shows a fuel supply system 100 , that with a volume flow-based pump-synchronous rail pressure control according to 2 is operated.

A high pressure pump 1 is by a feed pump 2 via a low pressure line 2.1 with fuel from a fuel tank 3 provided. In the low pressure line 2.1 is a filter unit 5 and a duo sensor 6th , the pressure p6 and temperature T6 in front of the high pressure pump 1 in the low pressure line 2.1 measures, arranged.

Via a high pressure line 1.4 pumps the high pressure pump 1 Fuel in a fuel reservoir, in particular in a fuel rail 4th . The fuel rail 4th includes a rail pressure sensor 7th , the rail pressure p7 in the fuel rail 4th detected.

The fuel rail 4th further comprises a pressure regulating valve 8th , which within the process a specifiable volume flow V8 via a return line 8.2.1 into the low pressure line 2.1 from the fuel rail 4th steers off.

Between the fuel rail 4th and the injectors 9n ; (n = 1, 2, 3 ...) 91, 92, 93, 94 are the injector lines 4.9 shown over which the injectors 9n be supplied with fuel.

The injectors 9n have leakage lines that lead into a common return line 9.3 flow out. The return line 9.3 opens into a high pressure pump return line 1.3 the high pressure pump 1 that go to the fuel tank 3 returns.

A control unit S1 , in particular an engine control unit, is directly connected to the duo sensor via control lines (without reference symbols) 6th , the high pressure pump 1 , the pressure control valve 8th , the rail pressure sensor 7th and the injectors 91 , 92 , 93 , 94 and in the exemplary embodiment indirectly via a control unit S2 with the pre-feed pump designed as a low-pressure pump 2 connected.

The 2 shows the volume flow-based pump-synchronous control structure for rail pressure control, which is in an electronic control unit, in particular the control unit S1 is stored, which is set up to carry out one of the methods presented above. The control unit S1 and the control unit S2 are operated via a computer program for executing the method, a machine-readable storage medium with the computer program recorded on it being provided on the computer.

The volume flow-based pump-synchronous control structure for rail pressure control is based on the 2 explained in detail below.

The basic idea of the method explained below for the future diesel engines, which are designed as common rail diesel engines, is that a required rail pressure of up to 2700 bar with the high pressure pump 1 by a predeterminable volume flow in the rail 4th is produced.

With a positive volume balance, i.e. increasing volume flow in the rail 4th the pressure in the rail increases 4th at. The rail pressure sensor 7th gives the control loop consisting of a pilot control model, a controller and an actuator of the high pressure pump 1 the corresponding print information.

The input variable of the method for operating the fuel supply system according to the invention 100 According to the invention, a certain volume flow is that of the high pressure pump 1 supplied or through the pressure control valve 8th is discharged.

The subject matter of the invention is thus that the complete high-pressure regulation, therefore, the rail-pressure-high-pressure regulation within the rail 4th of the fuel supply system 100 , from a time-based cyclical calculation of a rail pressure regulator to regulate the rail pressure in the rail 4th to a volume flow-based and pump-synchronous discrete calculation for rail pressure control (in a two-position concept pressure control valve control and high pressure pump control) based on the engine segment of the internal combustion engine.

For this purpose, it is necessary according to the invention to discretely describe the volume flows to be observed and the associated model of the control structure according to the invention.

The print information p7 _is from the rail pressure sensor 7th a motor-synchronous / pump-synchronous segment with the target rail pressure p7 _target of the preceding motor-synchronous / pump-synchronous segment (one speaks of the delayed setpoint rail pressure) compared to the discrete control difference Δp7 to determine.

This pressure difference Δp7 is about the modulus of elasticity E. of the fuel and by means of the duo sensor 6th determined fuel temperature T6 converted into a volume difference and used as an input variable AV _Rail processed in a controlled system.

This volume difference ΔV _rail with the help of the digital metering unit (not shown), which is preferably located in the pump chamber of the high pressure pump 1 is arranged or by controlling the pressure control valve 8th as input variable of the controlled system and the actuator of the high pressure pump 1 or the pressure control valve 8th are controlled, whereby the discretization, i.e. the calculation of the volume difference AV _Rail can be varied pump-synchronously for each motor segment.

For this purpose, a volume balance is created that physically reflects the pressure p7 _is in the rail 4th describes.

The volume balance of the volume flow-based segment-synchronous calculation is based on a volume-constant room volume V _H of Assumed high pressure system in which there is a certain volume of fuel depending on the pressure, which is basically via the high pressure pump 1 supplied and via the pressure control valve 1 is discharged.

The volume of the room V _H the high pressure system of the fuel supply system 100 includes the volume of the rail 4th , the volume of the injector lines 4.9 to the injectors 9n , the volume of space in the injectors 9n up to the throttle point within the injectors 9n , the supply line 1.4 the high pressure pump 1 to the rail 4th from the check valve in the supply line 4.9 and the dead volume of the high pressure pump 1 (Dead volume = Volume of space between TDC of the piston of the high pressure pump 1 and the check valve in the supply line to the rail 4th ).

1. a) aus den Kraftstoff-Einspritzmengen V_9n über die Injektoren 91, 92, 93, 94 und
2. b) den Kraftstoff-Schaltleckagen V_SLeck der Injektoren 91, 92, 93, 94 sowie der
3. c) der Kraftstoff-Dauerleckage V_DLeck des Hochdrucksystems des Kraftstoffversorgungssystems 100

zusammensetzt.Based on the volume of the room V _H the high pressure system of the fuel supply system 100 the high pressure system becomes a total volume synchronously with the segments V _Ges-Ab removed, which is a total

1. a) from the fuel injection quantities V _9n about the injectors 91 , 92 , 93 , 94 and
2. b) the fuel shift leaks V _SLeck the injectors 91 , 92 , 93 , 94 as well as the
3. c) the permanent fuel leakage V _DLeck of the high pressure system of the fuel supply system 100

composed.

The volumes a) and b) are taken on an event-related basis, while c) the permanent fuel leakage V _DLeck of the high pressure system is discretized via a Z transformation. This means that the non-event-related permanent leakage is converted V _DLeck of the high-pressure system takes place in an event-related segment-synchronous discrete volume. In other words, there is an event-related discretization of the permanent leakage V _DLeck of the high pressure system instead, so that the volumes a), b), c) correspondingly as taken from the high pressure system as the total volume V _Ges-Ab can be added.

Added to this is d) the so-called load and / or speed-dependent change request for the rail pressure, the so-called pressure change request (also referred to as the dynamic volume flow component) within the rail 4th , which is achieved by supplying fuel volume (pressure increase) via the high pressure pump 1 when V _{Δp rail specification} or by discharging the fuel volume (pressure reduction) via the pressure control valve 8th within the volume balance as V _{Δp rail specification} is taken into account.

• • bei einer Druckerhöhung ein segmentsynchrones Volumen V_Zu zu dem Gesamt-Volumen V_Ges-Ab addiert oder
• • bei einer Druckabsenkung wird ein segmentsynchrones Volumen V_Ges-Ab von dem Gesamt-Volumen V_Ges-Ab subtrahiert.

Depending on whether the pressure change request concerns an increase or decrease in pressure,

• • A segment-synchronous volume in the event of a pressure increase V _to to the total volume V _Ges-Ab added or
• • When the pressure drops, a segment-synchronous volume becomes V _Ges-Ab of the total volume V _Ges-Ab subtracted.

The high pressure pump 1 has a fixed assignment of the pump TDC segment-synchronous / cylinder-synchronous every 180 ° crank angle of the internal combustion engine to the cylinder piston TDCs of the cylinder piston (not shown) of the internal combustion engine in a known manner and advantageously, the engine speed corresponding to the high pressure pump speed. A certain fixed offset can exist between the pump TDC and the cylinder piston TDC, but this is known and can be taken into account accordingly in the fixed assignment.

This fixed assignment enables the volume flow-based and pump-synchronous discrete calculation for rail pressure control to be based and discretized on this synchronicity. This means that only a discrete subset is obtained from a continuous amount of data or information, which simplifies the calculation of the variables within the controlled system.

The calculation according to the invention takes place via a trigger start signal nsync (compare 2 ), the calculation being segment-synchronous / cylinder-synchronous every 180 ° crank angle, with the calculation of the variables of the controlled system for each of the cylinders or the associated injectors 9n which inject into this cylinder is carried out separately.

According to the 2 includes the volume flow-based pump-synchronous control structure for the rail pressure control of the high-pressure pump 1 a signal acquisition block B1 for signal acquisition of the rail pressure p7 by means of the rail pressure sensor 7th .

According to the invention, the rail pressure is detected p7 synchronously within the block B1 for signal acquisition of the rail pressure p7 in a measuring grid in ms steps, with within the segment within the module B2 , which is referred to as the actual value discretization module, an actual value is discreetly segment-synchronized p7 _is as the minimum pressure p _7actual-min and as the maximum pressure p _7actual-max are recorded and stored, from these pressures P _7actual-min , P _7actual-max also as the actual value p7 _is an average p7 _actual-50% of the pressures p _7actual-min , p _7actual-max is calculated within the segment and also saved.

According to the 2 includes the volume flow-based pump-synchronous control structure for the rail pressure control of the high-pressure pump 1 a setpoint specification block A1 for the setpoint specification of the rail pressure p7 _target which are stored in the form of map data in the computer program of the engine control unit, which comes from the respective applied combustion process and is specified.

This target rail pressure p7 _target is also discretized according to the invention from any current default time frame, that is, a conversion from the time “slices” into the segment “slices” takes place at the point in time nsync the (trigger start signal), i.e. at the beginning of the calculation.

This explicitly means that the first value present in the segment disk within the time pattern as the set rail pressure p7 _target Is “frozen” and thus discretized. This discretization takes place in the setpoint discretization module A2 instead of.

As a result, the target rail pressure p7 _target at the time nsync is "frozen" at the beginning of a time slice of the segment, the desired rail pressure from the previous segment lies p7 _target (End of the previous segment = Start next segment at the time nsync ) and is discretized with the print information p7 _is from the rail pressure sensor 7th discretized and compared from the current segment, i.e. the following segment, within a working cycle, creating a discrete control difference Δp7 can be determined per segment (segment-synchronous). This procedure is necessary because the system always has a time delay. The control value of a pilot control generates an increase in volume flow into the rail after the pump has delivered. Therefore, the setpoint used to form the difference is used p7 _target delayed by exactly one working cycle and with the actual value p7 _is of the following work cycle compared.

As explained above, there is a discrete actual value p7 _is the minimum pressure p _7min or the maximum jerk p _7max or the mean value p7 _50% are available.

Advantageously, there is the possibility within the regulation (selection of several discrete signals from the setpoint discretization module A2 ) for control as an actual value p7 _is the minimum discrete pressure p _7Ist-min or the maximum discrete pressure p _7Ist-max or the discrete mean value p7 _actual-50% to use to match the selected value with the discrete target rail pressure p7 _target to compare, whereby depending on the system requirements the value p7 _{actual max} and the value in the event of a pressure reduction p7 _{actual min} is used to reduce control oscillations or to avoid overshoots or undershoots. The corresponding pressure-related calculation takes place in the control error calculation module A2 / B2 (compare 2 ) into the discretized setpoint rail pressure values p7 _target and the discretized actual rail pressure values p7 _is received and compared segment-synchronously and output and saved calculated as a control error.

At this point, the control error calculation is carried out according to the invention in a conversion module A2 ', B2' from the pressure-based, discretized control difference Δp7 = Δp _rail a conversion into a volume flow-based control difference ΔV _rail , that is, a volume flow difference with the solution of a differential equation, where E is the pressure and temperature-dependent specific modulus of elasticity of the respective fuel and V _H as previously explained, the volume of space of the high pressure fuel system of the fuel supply system 100 are. $$\Delta {\text{V}}_{\text{Rail}}=\frac{V_{\text{H}}}{\mathrm{E.}\left(p,T\right)}\ast \Delta {\text{p}}_{\text{Rail}}$$

This conversion into the segment-synchronous volume error ΔV _rail has the advantage that the non-linear fuel properties of the fuel are taken into account in the regulation.

The non-linear properties of the fuel in terms of pressure, temperature and compressibility are not mapped in pressure-based systems, which is a significant advantage of the present method, since these non-linearities are converted into segment-synchronous volume errors AV _Rail be taken into account.
This enables precise control and regulation with the smallest control errors even in highly dynamic driving situations, which results in decisive advantages in terms of combustion stability and emissions.

As an intermediate summary, compared to the prior art, there is therefore a change in the detection of the variables due to the segmentation in the modules A1 , B1 and the discretization in the building blocks A2 , B2 and a conversion of pressure-based quantities to volume-flow-based quantities in the modules A2 / B2 such as A2 '/ B2' in front.

As an input variable for a controller module C. , C1 , C8 there is thus a discrete volume control difference in the basic concept according to the invention AV _Rail available directly for the volume flow-based actuators E1 , E8 ( high pressure pump 1 and pressure control valve 8th ) is used. An extension, the “cylinder-selective control”, will be discussed in detail below under the subheading of the same name.

The controller component C. , C1 , C8 includes a controller state machine as a component C. which, depending on the requirements, the pressure based on volume flow / volume flow, i.e. depending on the discrete in the conversion module A2 '/ B2' determined volume control difference ΔV _rail increases or decreases, and it decides whether a control intervention via a PID controller block C1 the high pressure pump 1 (compare 2 ) "Pressure increasing" or via a PID controller block C8 of the pressure control valve 8th Should take place “lowering the pressure”.

The structure also includes according to 2 a pre-control volume flow value module D. as a fault controller for the segment-synchronous volume flow-based precontrol (reference variable with disturbance variable compensation) of the fuel supply system, its reference variable with the PID controller module C1 the high pressure pump 1 and the PID controller block C8 of the pressure control valve 8th is brought together so that the PID controller modules C1 , C8 only have to compensate for the control fluctuations of the fuel supply system.

The pre-control volume flow value block D. the segment-synchronous volume flows mentioned under a) to d) are added as pre-control variables, so that in the pre-control volume flow value module D. the management of the controlled system is already guaranteed.

The through the PID controller blocks C1 , C8 Corrected values of the fault controller of the precontrol volume flow value block D. become (compare 2 ) an output module E. fed to the actuators E1 and E8 the high pressure pump 1 and the pressure control valve 8th electrically controls and the actuators E1 and E8 Adjusted pump segment-synchronously based on volume via the controlled system as required.

• Erfindungsgemäß wird die zuvor hinsichtlich der Grundkonzeption erläuterte Raildruckregelung auf eine sogenannte „Zylinderselektive Regelung‟ erweitert, wie nachfolgend erläutert wird.

Extension "cylinder selective control":

• According to the invention, the rail pressure control explained above with regard to the basic concept is extended to a so-called “cylinder-selective control”, as will be explained below.

For this purpose, n = number of cylinders or the associated injectors for each cylinder 9n (compare 1 ) a separate cylinder-selective control deviation ΔV _rail , in particular a proportional component and / or an integrator component and / or a differential component are calculated and based on the cylinder-selective control deviation AV _Rail the control values E1 , E8 Cylinder for cylinder or injector for injector 9n or injection valve for injection valve selected segment-synchronously and, as explained above, based on volume flow for the high-pressure pump 1 or the pressure control valve 8th issued.

As the injectors 9n In steady-state operation, the same target volume values are obtained from cylinder to cylinder, but different volume decreases result from injector scatter V _9n from the rail 4th show, according to the invention, for example, the individual integrator components of the cylinder-selective controllers C1 _n , C8 _{n show} the quantity deviations between the injectors 9 _n , which can have various causes. Depending on the type of quantity discrepancy, the causes can be assigned to specific error groups with a high degree of probability.

According to 2 is the input variable for a controller block C. , C1 , C8 thus a discrete volume control difference in the basic concept according to the invention AV _Rail available directly for the volume flow-based actuators E1 , E8 (High pressure pump 1 and pressure control valve 8th ) is used, with segment-synchronous for each cylinder or injector 9n "Only one" rule structure is used repeatedly. An extension, the so-called “cylinder-selective control”, in which several control structures are used cylinder-selectively, is discussed in detail below under the subheading of the same name.

Analogous to the basic concept, there is a segment-synchronous discrete volume control difference as the input variable for several (n) controller modules C1n, C8n ΔVRail are available which, according to the extension, are cylinder-selective directly for the volume flow-based actuators E1 , E8 (High pressure pump 1 and pressure control valve 8th ) is used.

Per cylinder or injector 9n are available as sub-modules of a controller state machine C. are assigned, several controller modules C1n (in the exemplary embodiment n = 4; C11, C12, C13, C14), C8n (in the exemplary embodiment n = 4; C81, C82, C83, C84) are available which, depending on the segmental requirement, the pressure Volume flow based / volume flow based, i.e. depending on the in the conversion module A2 '/ B2' determined discrete volume control difference ΔV _rail increase or decrease, with the controller state machine C. it decides whether the control interventions are segment-synchronized via several PID controller modules C1n of the high-pressure pump 1 (compare 2 ) "Pressure increasing" or via several PID controller modules C8n of the pressure control valve 8th Should be carried out “pressure-lowering” in a cylinder-selective manner.

The structure also includes according to 2 a pre-control volume flow value module D. as a fault controller for the segment-synchronous volume flow-based precontrol (reference variable with disturbance variable compensation) of the fuel supply system 100 , its reference variable with the PID controller block C1n of the high pressure pump 1 and the PID controller modules C8n of the pressure control valve 8th is brought together so that the PID controller modules C1n, C8n only have to compensate for the control fluctuations of the fuel supply system.

• Die Hochdruckregelung kann durch die zylinderselektive Regelung zylinderselektiv geführt werden, das heißt jedem Zylinder beziehungsweise jedem Einspritzvorgang wird zylinderselektiv eine angepasste zylinderselektiv korrigierte Stellgröße als Stellgliedausgabe E1 der Hochdruckpumpe 1 oder Stellgliedausgabe E8 des Druckregelventils 8 ausgegeben.

This results in the following effects:

• The high-pressure control can be performed cylinder-selectively by the cylinder-selective control, that is, for each cylinder or each injection process, an adapted, cylinder-selectively corrected manipulated variable is output as actuator output E1 the high pressure pump 1 or actuator output E8 of the pressure control valve 8th issued.

In other words, the respective PID controller modules C1n, C8n can each be evaluated separately and calibrated. The evaluation of the four individual PID controller modules C1n or C8n in the exemplary embodiment, i.e. the comparison of the integrator components and proportional components that are different in steady-state operation, for example, allows a cylinder-related or injector-related error analysis and cause grouping, on the one hand Simple diagnostic function (on-board diagnosis without expansion) or a diagnostic function (on-board diagnosis without expansion) with a correction function is provided.

For example, a specific cylinder-related or injector-related error can be permitted up to a predefinable threshold value via the diagnostic function, and a cylinder-related or injector-related error correction only takes place after the threshold value has been exceeded.

According to the invention, there is in particular the possibility of grouping the injection quantity errors depending on the cause, with the injectors 9n For example, in the operation of an error group with an injector defect (on-board diagnosis of an injector defect without removal), or another error group with an age-related injector drift (on-board diagnosis of injector drift without removal) or another error group with a changing amount of switching leakage V _SLeck (OnBoard diagnosis of an excessively high switching leakage without removal) can be assigned, with the injection quantity errors advantageously within the OnBoard diagnosis for an exchange of the defective injector 9n or can be taken into account and corrected within the cylinder-selective control.

In addition, the cylinder-selective control information, i.e. the individual injection quantity errors of the individual injectors, can generally be used 9n can be adapted and to improve the feedforward control D. the injectors 9n be used.

The respective cylinder-selective controlled variable C1n, C8n can also advantageously be converted into another reference variable, with particular consideration being given to the internal engine torque of the respective cylinder, so that a cylinder-selective torque-dependent control is made possible through the support of the cylinder-selective rail pressure control, in which the cylinder-selective control information in particular can be used for torque-cylinder equalization by, for example, transferring a corresponding pilot control value from the cylinder-selective rail pressure regulation to a cylinder-selective torque controller.

List of reference symbols

100

Fuel supply system

1

high pressure pump

2

Feed pump

3

Fuel tank

4th

Fuel storage, rail

AV _Rail

Volume control difference, discrete control deviation

5

Filter unit

6th

Duo sensor (p, T)

T6

Fuel temperature

7th

Rail pressure sensor

p7

Rail pressure

p7 _is

Actual rail pressure

p7 _{actual max}

Actual rail pressure (discretized max)

p7 _{actual min}

Actual rail pressure (discretized Min)

p7 _actual-50%

Actual rail pressure (discretized mean value)

p7 _target

Target rail pressure (discretized)

Δp7 = Δp _rail

discrete control deviation (pressure-related)

E.

modulus of elasticity

8th

Pressure control valve

V8

controlled volume flow via return line 8.1

9n

Injectors (n-th injector)

91

first injector

92

second injector

93

third injector

94

fourth injector

1.4

High pressure line between 1 and 4

2.1

Low pressure line between 2 and 1

4.9

Injector lines between 4 and 9n

8.2.1

Return line between 8 and 2.1

9.3

Leak return line between 9n and 3

1.3

HDP return line between 1 and 3

S1

first control unit

S2

second control unit

V _Ges

Total volume ( V _9n + V _DLeck + V _{SLeck +} V _{Δp rail specification} )

V _9n

Injection volume of the respective n-th injector 9n

V _DLeck

Continuous leakage volume flow of the high pressure fuel supply system

V _SLeck

Switching leakage volume flow of the injectors 9n

V _{Δlip-rail specification}

System-related pressure change request

V _TO

Supplied volume depending on the pressure change desired pressure increase

V _Ges-Ab

Volume discharged as a function of the pressure change request Pressure reduction

V _H

constant volume of the high pressure fuel supply system

nsync

Start time of the calculation

A1

Setpoint specification block of the rail pressure p7 _target

A2

Setpoint discretization module

B1

Actual value signal acquisition module rail pressure p7 _Is

B2

Actual value discretization module

A2 / B2

Control error calculation module

A2 '/ B2'

Conversion module

C.

State machine controller block

C1

Standard building block of the high pressure pump

C8

Control module of the pressure control valve

D.

Input tax module

E.

Output block

E1

Actuator output high pressure pump

E8

Actuator output pressure control valve

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102016204386 A1 [0002]

Claims (13)

Method for regulating a rail pressure (p7 _setpoint ) for a fuel supply system (100) of an internal combustion engine caused by a high-pressure pump (1) in a fuel accumulator (4), wherein a crank angle-related or cam angle-related fixed angle difference of the internal combustion engine between a top dead center position of a cylinder piston of a Cylinder of the internal combustion engine and a top dead center position of the pump piston of the high pressure pump (1) of the fuel supply system (100) is taken into account when metering the delivery volume of the high pressure pump (1), characterized in that recurring pump synchronism per segment, which is one revolution of a crankshaft and thus the movement of the pump piston of the high-pressure pump (1) from the top dead center position of the pump piston to the next top dead center position corresponds to a discretization of a control deviation (Δp ₇ ) of the rail pressure (p7) in the fuel accumulator (4) and made by the discrete rules a deviation (Δp ₇ ), a volume-related discrete volume control difference (ΔV _Rail ) is calculated for each cylinder. Procedure according to Claim 1 , characterized in that the volume-related discrete volume control difference (ΔV _Rail ) is fed as cylinder-selective input variables to a control module (C1n) for the high-pressure pump (1) and a control module (C8n) for a pressure control valve (8) assigned to the fuel accumulator (4), The discrete volume control difference (ΔV _Rail ) is linked to a pilot control module (D), which calculates the manipulated variables for the high-pressure pump (1) and the pressure control valve (8) in an output module (E8) for each segment in a pump-synchronized and cylinder-selective manner and the actuators (E1, E8) of the high pressure pump (1) and the pressure control valve (8) for volume-based, cylinder-selective adjustment of the rail pressure (p7 _target ). Procedure according to Claim 1 , characterized in that the discrete control deviation (Δp ₇ ) as the difference between the discretized actual rail pressure (p7 _actual ) and the discretized target rail pressure (p7 _target ) is calculated cylinder-selectively by using discretized pressure information (p7 _actual ) from a rail pressure sensor (7) of the actively detected pump-synchronous segment is compared with the discretized target rail pressure (p7 _target ) of the pump-synchronous segment preceding by one work cycle in order to determine the discrete cylinder-selective control difference (Δp7). Procedure according to Claim 3 , characterized in that the target rail pressure (p7 _target ) is discretized at a point in time which is determined with a trigger start signal (nsync) which is output repeatedly at the beginning of a pump-synchronous segment. Procedure according to Claim 3 and 4th , characterized in that the actual rail pressure (p7 _actual ) is recurrently recorded and discretized within the segment started by the trigger start signal (nsync). Procedure according to Claim 5 , characterized in that the actual rail pressure (p7 _Ist ), which is recurrently recorded within the pump-synchronous segment, as • in the segment maximum actual rail pressure (p7 _{actual max} ) and • in the segment minimum actual rail pressure (p7 _{actual -min} ) and • mean value calculated in the segment (p7 _actual-50% ) is discretized and optionally compared with the discretized target rail pressure (p7 _target ) to determine the discrete cylinder-selective control deviation (Δp7). Procedure according to Claim 6 , characterized in that the recorded minimum discrete pressure (p _7actual-min ) or the recorded maximum discrete pressure (p _7actual-max ) or the discrete mean value (p7 _actual-50% ) are used as the actual value (p7 _actual ) for the cylinder- _{selective control} ) is used for comparison with the discrete target rail pressure (p7 _target ), whereby, depending on the system requirements, the maximum discrete pressure (p _7actual-max ) is used for a pressure _build-up and the minimum discrete pressure (p _7actual-min ) for a pressure reduction, to reduce control oscillations for each cylinder or to avoid overshoots or undershoots. Procedure according to Claim 6 or 7th , characterized in that the discrete cylinder-selective control deviation (Δp ₇ ) is converted into the volume flow-based discrete cylinder-selective volume control difference (ΔV ₇ = ΔV _Rail ), with a permanent fuel leakage (V _DLeck ) of the high-pressure system of the fuel supply system being taken into account by addition. Procedure according to Claim 1 , characterized in that the pressure-based, discretized, cylinder-selective control difference (Δp7 = Δp _Rail ) is converted into a volume flow-based, cylinder-selective volume control difference (ΔV _Rail ), the pressure- and temperature-dependent specific modulus of elasticity (E) of the respective fuel and the volume of the space being converted (V _H ) of the high-pressure fuel system of the fuel supply system (100) according to the conversion formula $\Delta {\text{V}}_{\text{Rail}}=\frac{V_{\text{H}}}{\mathrm{E.}\left(p,T\right)}\ast \Delta {\text{p}}_{\text{Rail}}$

is considered cylinder-selective. Procedure according to Claim 9 , characterized in that in the pump-synchronous, segment-wise recurring conversion of the pressure-based discrete cylinder-selective control deviation (Δp7) into the volume-related discrete volume control difference (ΔV _Rail ), a) cylinder-selective the fuel injection quantities (V _9n ) of the injectors (9n) and b) cylinder- _selective the fuel switching _leakages (V _SLeck ) of the injectors (9n) and d) cylinder- _selective a pressure change request (V _{Δp rail specification} ) with respect to the target rail pressure (p7 _target ) of the fuel accumulator (4) is taken into account, with c) the fuel Permanent leakage (V _DLeck ) of the high pressure system of the fuel supply system (100) is determined by a pump-synchronous, segment-wise recurring separate conversion with a Z-transformation and added to the volume-related discrete volume control difference (ΔV ₇ = ΔV _Rail ). Procedure according to Claim 10 , characterized in that the injectors (9n) in steady-state operation from cylinder to cylinder receive the same quantity setpoints, which are compared cylinder-selectively with the quantity decreases (V _9n ) from the rail (4), with cylinder-selective injection quantity _errors that the injectors (9 _n ) can be assigned, one type of quantity discrepancy being assigned to specific error groups. Procedure according to Claim 11 , characterized in that the injection quantity errors are grouped depending on the cause, in particular depending on the level of the injection quantity error resulting from the target / actual comparison, the injectors (9n) during operation of an error group with an injector defect, an error group with an age-related injector drift or a Error group with a changing switching _{leakage quantity} (V _SLeck ) can be assigned, whereby the injection _{quantity errors} are determined within the cylinder- _selective control in the controller (C1 _n , C8 _n ) and corrected in the injection system and / or for an exchange of the respective injector / injectors (9n) ) to lead. Fuel supply system (100) set up to carry out the method according to at least one of Claims 1 to 10 , characterized in that the fuel supply system (100) • to determine the respective discrete input variable of the respective cylinder cylinder-selective several (n) controller modules (C1n) for the high pressure pump (1) and to determine the respective discrete input variable of the respective cylinder cylinder-selective several ( n) controller modules (C8n) for a pressure control valve (8) assigned to the fuel accumulator (4), and • a setpoint specification module (A1) for the rail pressure (p7 _setpoint ) and an associated setpoint discretization module (A2) and • a Actual value signal acquisition block (B1) of the rail pressure (p7 _Ist ) and an actual value discretization block (B2), • and a control error calculation block (A2 / B2) and • a conversion block (A2 '/ B2' ), which converts a pressure-based discretized control difference (Δp7 = Δp _Rail ) into a volume flow-based control difference (ΔV _Rail ), where • the conversion module (A2 '/ B2') with a controller state machine (C) is linked, which outputs the discrete input variable cylinder-selectively to the respective controller module (C1n) of the high pressure pump (1) and the discrete input variable cylinder-selectively to the respective controller module (C8n) of the pressure control valve (8), • where the controller modules (C1n, C8n) are each cylinder-selectively linked with a pilot control module (D), whereby the control variables are pump-synchronously per segment by means of the pilot control module (D) and the connected cylinder-selective controller modules (C1, C8) for the high pressure pump (1) and the pressure regulating valve (8) are fed to an output module (E8) and calculated, and the actuators (E1, E8) of the high pressure pump (1) and the pressure regulating valve (8) for volume-based, cylinder-selective adjustment of the rail pressure ( p7 _target ) are supplied.

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