DE102016200713A1 - Method for controlling intake manifold injection for an internal combustion engine with combined intake manifold injection system and direct injection system - Google Patents

Abstract

The invention relates to a method for controlling a port injection of an internal combustion engine associated fuel injection system with a port injection system and a direct injection system with a common low-pressure fuel system (4), wherein an injection valve (13) of the port injection system during a determined by an electronic control unit (20) driving the During a current operating point of the internal combustion engine and the fuel injection system by the electronic control unit (20), the drive duration (TE1, TE2) of the injection valve based on a previously operating point specifically measured in the engine operation and the current operating point associated fuel pressure curve is determined.

Description

The invention relates to a method according to the preamble of independent claim 1. The invention also relates to an electronic control unit, a computer program and a storage medium.

State of the art

In today's internal combustion engines find fuel injection systems with a combined intake manifold injection system and direct injection system use. These are also referred to as PDI systems. In a PDI system, the intake manifold injection system constructed as a low-pressure injection system is supplied with fuel, in particular gasoline, directly from the low-pressure fuel system or low-pressure circuit. By contrast, the direct injection system is designed as a high-pressure injection system with a high-pressure pump whose inlet and outlet are coupled to the low-pressure fuel system common to both injection systems.

The injection quantity of an injection valve of the intake manifold injection system is generally calculated from a fuel pressure applied to the low-pressure fuel distributor or low-pressure rail and the opening duration or activation duration of the injection valve. In the low-pressure fuel system occurring fuel pressure fluctuations, which are caused for example by the opening and closing of the cylinder-specific injection valves of the intake manifold injection system, therefore, lead to deviations between the predetermined and the actually delivered intake manifold injection quantity. In PDI systems with a common low-pressure fuel system, the aggravating factor is that the high-pressure pump driven by an engine camshaft generates pressure fluctuations in the low-pressure fuel system. In particular, in demand-controlled fuel supply systems, a high-pressure pump is provided with a quantity control valve for adjusting the fuel delivery rate or the required high-pressure fuel. The mass control valve allows unused fuel from the high pressure injection system to be delivered from the high pressure pump back to the low pressure fuel system. This back-pumping, which always occurs per Pumpenkolbenhub except for a full promotion of the high-pressure pump, as well as the filling of the pump chamber of the high-pressure pump with fuel and a fast opening and closing of the quantity control valve cause pressure fluctuations in the low-pressure fuel system. Even when the high-pressure pump is deactivated, that is to say with pure intake manifold injection, and during overrun operating phases of the internal combustion engine without injection, the pressure fluctuations caused by the pumping back of the high-pressure pump operated in zero delivery occur.

Disclosure of the invention

Against this background, a method and an electronic control unit with the features of the independent claims are presented. Further embodiments will be apparent from the dependent claims and the description.

In the presented method is provided for controlling a port injection of a fuel injection system of an internal combustion engine with a port injection system and a direct injection system with a common low-pressure fuel system that during a current operating point of the internal combustion engine and the fuel injection system, in particular by an electronic control unit, a driving duration of an injection valve of the port injection is determined on the basis of a previously measured in the engine operating point specific measured and the current operating point associated fuel pressure curve. During the operation of the engine provided with the fuel injection system, the fuel pressure profile is determined, in particular in the form of a fuel pressure curve value series, and thus not offline only for a reference engine operated on an engine test bench. A respective fuel pressure curve value series describes a course of the fuel pressure determined by a plurality of fuel pressure measurements over a time interval, wherein the fuel pressure per injection cycle of a cylinder is repeatedly measured or determined.

The method is preferably used in a PDI system with a demand-controlled fuel supply system, in which a high-pressure pump assigned to the direct injection system is provided with a volume control valve for adjusting the fuel delivery rate or the required high-pressure fuel. The method is used in particular for gasoline injection systems.

With the presented method, the deviation between the fuel quantities to be injected and injected by the intake manifold injection system can be reduced. Accuracy of injection port injection and possibly simultaneous direct injection injection is thus improved. As a result, the exhaust behavior, smoothness and fuel consumption of the internal combustion engine with active intake manifold injection are improved.

In a refinement of the method, it is provided that determination of the activation duration takes place on the basis of an assignment, determined in advance specifically during engine operation, between a plurality of fuel pressure profile value series measured in the low-pressure fuel system and a plurality of operating point-specifying data records.

In a further development of the method, it is additionally provided that a respective fuel pressure profile value series has been determined by means of high-frequency measurement of fuel pressure fluctuations caused by operation of the intake manifold injection system and / or the direct injection system with a pressure sensor arranged in the low-pressure fuel system. High-frequency means for this development that the fuel pressure curve per injection stroke of the injection valve associated cylinder of the internal combustion engine is detected sufficiently often to detect per injection stroke the detected pressure fluctuations as time-dependent pressure wave or pressure pulsation can. In this development, the pressure sensor already provided in conventional demand-controlled fuel supply systems can be used efficiently for determining the allocation.

In a further development of the last-mentioned further development, it is provided that a respective fuel pressure curve value series specifies the measured fuel pressure fluctuations as a fuel pressure wave, wherein the fuel pressure profile value series is specified in terms of value by a frequency, a phase and an amplitude or damping of the fuel pressure wave. The phase is related to a crankshaft angle and / or an opening or closing time of an injection valve of the fuel injection system. At the same time, this ensures an exact and implementation-favorable determination of the activation duration.

In one development of the method, it is provided that each operating point of the internal combustion engine and of the fuel injection system used for determining the activation duration, to which a respective unique operating point specifying data record is assigned, by a rotational speed and a torque of the internal combustion engine and at least one determined operating parameter value of the fuel injection system from the group is specified by a temperature of the fuel in the low-pressure fuel system, a viscosity of the fuel, a compression modulus of the fuel, and a combustion property of the fuel. The temperature of the fuel in the low pressure fuel system may be directly sensed as a temperature sensor value or may be derived from other sensor values and / or operating parameters by a thermal model. The combustion characteristic of the fuel may be detected by means of a fuel quality sensor or may be determined by known methods, such as octane determination in the context of anti-knock control, determination of changed pressure wave propagation times or changes in combustion chamber pressure history or stored in a controller. Based on the operating point of the internal combustion engine, the injection quantity is predetermined, which can be divided into a port injection proportion and / or a direct injection rate in PDI systems.

In a general development of the method, it is provided that the assignment during operation of the internal combustion engine provided with the fuel injection system is determined or learned using a learning method. The learning is preferably repeated with a time interval. As a result, changes caused by drifting, aging and tolerances of the components of the fuel supply and injection system can be compensated with regard to the previously determined fuel pressure profiles, so that exact injection quantities are ensured even over a long period of operation.

On the basis of the last-mentioned general development, it is further provided that the assignment is updated at predetermined time intervals by means of a weighted and / or filtered learning, and that a fault in the low-pressure fuel system is detected if an extent of an update of the assignment exceeds a predetermined threshold , As a result, compliance with the specified injection quantity can be ensured even better.

In a further development of the mentioned general development, it is provided that the learning of the assignment takes place in a first operating phase type of the internal combustion engine with inactive intake manifold injection and active direct injection. This is particularly advantageous if the high-pressure pump significantly causes the pressure fluctuations influencing the injection quantity, and the pressure fluctuations caused by the intake manifold injections have only a small effect on the injection quantity, or the influence of the pressure fluctuations triggered by the intake manifold injections is learned separately, as in the next described training is provided. In the present development, the pressure fluctuation or the pressure wave is dependent on the opening and closing time (or the respectively associated crankshaft angle) of the quantity control valve of the high-pressure pump. With knowledge of the time interval of the opening and / or closing time of the quantity control valve of the high-pressure pump (or the Crankshaft angle of the internal combustion engine or a Förderternockenwellenwinkels the high pressure pump) for the subsequent injection start of each intake manifold injection valve, the amplitude profile of the pressure wave during the injection can be predicted or predicted and the driving time of the port injection valve to be corrected in advance to achieve the predetermined injection quantity. A correction of the injection quantity by means of a correction of an activation duration of the intake manifold injection valve determined offline with a reference engine thus takes place only with regard to the pressure fluctuations in the common low-pressure fuel system caused by the high-pressure pump.

In a further development of the mentioned general development, it is provided that the learning of the assignment takes place in a second operating phase type of the internal combustion engine with active intake manifold injection and inactive direct injection. This is particularly advantageous if the intake manifold injection significantly causes the pressure fluctuations influencing the injection quantity. The pressure fluctuation or the pressure wave is dependent on the opening and closing time (or the respectively associated crankshaft angle) of the other injection valves of the intake manifold injection system on the common low-pressure fuel system. The pressure fluctuation or pressure wave caused by the high-pressure pump is dependent only on the pumping volume of the high-pressure pump, which is operated in the case of inactive direct injection in zero delivery. The amount sucked in by the high-pressure pump is completely returned to the low-pressure fuel system. A relative position of the pump piston and thus also the course of the pressure fluctuation is directly dependent on the conveyor cam and thus on the crankshaft angle and the speed of the internal combustion engine. With this development, changes in the pressure fluctuation behavior are advantageously adapted to an activation duration of the intake manifold injection valve determined offline by drifting, aging and tolerances of the components of the fuel supply and injection system arranged in and on the low pressure system. Correction of an actuation duration of the intake manifold injection valve determined offline with a reference engine thus takes place later in engine operation with regard to the pressure fluctuations caused by the high pressure pump operated in zero delivery and the pressure fluctuations in the common low pressure fuel system caused by the intake manifold injection.

In a further development of the mentioned general development, it is provided that the learning of the assignment takes place in a third operating phase type of the internal combustion engine with active intake manifold injection and active direct injection. This is particularly advantageous if both the high-pressure pump and the intake manifold injections significantly cause the pressure fluctuations influencing the injection quantity. The pressure fluctuations caused are a superposition of the pressure fluctuations depending on the opening and closing time (or the associated crankshaft angle) of the intake manifold injection and depending on the opening and closing time (or the associated crankshaft angle) of the quantity control valve of the high-pressure pump on the common low-pressure fuel system. Correction of an activation duration of the intake manifold injection valve determined offline with a reference engine thus takes place later in engine operation with regard to the pressure fluctuations caused by the high-pressure pump and the pressure fluctuations in the common low-pressure fuel system caused by the intake manifold injection.

The developments with the learning of the assignment in the first, second and third operating phase types can be used alone, for example with respect to the third operating phase type, as well as in temporally successive combination, for example with regard to the first and second operating phase types.

In a development of the method, it is provided that the assignment is stored as a table in a memory or by training a numerical model. In this case, the assignment after the measurement of the fuel pressure profile value series can be subjected to a numerical interpolation in order to break down the fuel flow value series and / or the operating point specifying data records of the operating parameters more closely or more uniformly. As a result, the accuracy of the delivered injection quantity can be improved in terms of implementation.

In a further development of the method using the assignment, it is additionally provided that a time interval for triggering the injection valve is determined on the basis of the assignment, for which an increased fuel pressure or fuel pressure wave peak in the common low-pressure fuel system is predicted on the basis of the assignment. Preferably, a maximum of the fuel pressure predicted on the basis of the assignment lies in this time interval. Thereby, fuel pressure increases or fuel pressure wave peaks of the fuel pressure fluctuations can be advantageously used to relieve a Kraftstoffvorförderpumpe, and to reduce an electric power required for driving the Kraftstoffvorförderpumpe.

In one development of the method, it is provided that the actuation duration of the injection valve is determined by a predetermined reference value and a correction value for the consideration of fuel pressure fluctuations in the common low-pressure fuel system, the correction value being based on the fuel pressure profile previously assigned to the operating point specifically in engine operation and assigned to the current operating point the fuel pressure history value series is determined. The fuel pressure curve or the fuel pressure profile-value series or the assignment makes it possible with particular advantage to determine or calculate a correction value for future pressure fluctuations or pressure waves caused by the intake manifold injection and / or the direct injection. This correction value can then be used for a correction of an activation duration of the intake manifold injection valve determined offline with a reference engine, which is stored in the electronic control unit as a reference model or basic application, to be used in the future for a corrected activation duration of the injection valve. Thereby, the effects of the fuel pressure fluctuations can be compensated efficiently, and the predetermined amount of fuel injection can be more precisely maintained.

In a further development of the method, it is provided that, for a plurality of injection valves of the intake manifold injection system, their respective activation periods are determined individually for an identical operating point of the internal combustion engine and the fuel injection system on the basis of the fuel pressure curve or the fuel pressure profile value series previously assigned to the identical operating point specifically during engine operation and specifically measured during engine operation. Thereby, the accuracy of the intake manifold injection is improved for all cylinders of the internal combustion engine.

The presented developments of the method can be combined with each other to obtain further advantageous development of the method.

There is further provided an electronic control device adapted to carry out one of the methods presented above. The method may be implemented in this controller as software or hardware or in a hybrid of software and hardware.

In addition, a computer program for executing the method on a computer and a machine-readable storage medium with the computer program recorded thereon are provided.

Brief description of the drawings

To clarify the above-described method, an embodiment with reference to exemplary figures will now be presented.

1 shows an example of a schematic representation of a PDI system whose intake manifold injection system can be controlled by the presented method.

2 FIG. 10 illustrates fuel pressure fluctuations occurring in a PDI system in the common low-pressure fuel system for two different operating points and an extended or reduced drive duration of an injection valve determined according to an embodiment of the presented method.

Embodiment of the invention

In 1 is a PDI system shown schematically, the intake manifold injection system can be controlled by the proposed method. In a fuel tank 1 absorbed fuel 2 is via an electric fuel pump 3 through a low-pressure fuel line 4 to a low-pressure rail 6 and to a high pressure pump 5 promoted a direct injection system. The low-pressure fuel line 4 and the low-pressure rail 6 together form a low-pressure fuel system. The high pressure pump 5 promotes via a high pressure line 7 Fuel to a high-pressure rail 8th to supply a high pressure injection valve with a predetermined fuel pressure 9 to supply fuel as the fuel quantity 10 in a combustion chamber 11 a cylinder 12 of the internal combustion engine is injected. To achieve the predetermined pressure, the high-pressure pump 5 or her in 1 not shown quantity control valve from an electronic control unit 20 regulated. If the high pressure pump 5 is not in Vollförderbetrieb, pumps the high-pressure pump 5 a partial fuel quantity back into the low-pressure fuel line 4 the common low-pressure fuel system, which is the low-pressure rail 6 and thus also an associated injection valve 13 the intake manifold injection system supplied with fuel.

An opening and closing of the injector 13 the intake manifold injection system is from the electronic control unit 20 so controlled that in the low-pressure rail 6 stored fuel through the opened injection valve 13 in a suction pipe 14 as a predetermined amount of fuel 15 is injected. The suction tube 14 is an inlet valve 16 of the cylinder 12 upstream. The activation duration or opening duration of the injection valve 13 is for the current operating point of the electronic control unit 20 according to the presented Method determined. So that the electronic control unit 20 is informed about the current operating point of the internal combustion engine and the fuel injection system, the control unit 20 externally acquired operating parameter data 17 fed. Corresponding operating parameter data can also be provided by the electronic control unit 20 be deduced even.

So that the fuel pressure present in the common low-pressure fuel system can be measured, the low-pressure rail 6 with a pressure sensor 18 provided via a measured value line 19 with the electronic control unit 20 connected is. With the pressure sensor 18 can be detected by high-frequency measurements of the fuel pressure in the low pressure system operating point specific fuel pressure curve value series according to an embodiment of the presented method in the electronic control unit, so that an association between a plurality of fuel pressure gradient value series and a plurality of operating point specifying data sets by the electronic control unit according to developments of the presented method can be determined and can be used to determine a control period of an injection valve of the intake manifold injection system. The time profile of the measured fuel pressure values is in the sense of a measured phase of a pressure wave to a crankshaft angle 21 or a relative position of the piston 22 of the internal combustion engine or opening and closing times of the injection valve 13 based.

In 2 is in section A by a bar 30 a predetermined by a conventional injector control method drive duration or opening duration TE an injection valve of the intake manifold injection system shown. In all sections A to D of 2 horizontally the time or a crankshaft angle is plotted.

In section B of 2 In the low-pressure fuel system occurring pressure curves are symbolically illustrated, wherein the pressure profiles shown in section B occurring in the low-pressure system phenomena only qualitatively illustrate and are at least quantitatively detached from the pressure curves shown in sections C and D. The curve sections 50 . 50A . 51 and 51A represent a pressure curve in the low-pressure fuel system with active intake manifold injection. The curve sections 50B and 51B on the other hand, represent a fictitious pressure curve as wave crest or wave trough in the low-pressure fuel system without active intake manifold injection. Section B of 2 illustrates that for the illustrated for the non-active port injection fictitious Wellenberg 50B the pressure curve present during active intake manifold injection 50A to a higher level than compared to the fictitious wave trough illustrated for non-active port injection 51B with the pressure drop present according to the curve section when the intake manifold injection is active 51A the case is. Therefore, the pressure waveform according to the curve sections 50 . 50A in comparison to the pressure curve according to the curve sections 51 . 51A with the same intake manifold valve control to a larger injection quantity.

In section C and section D of 2 are to the left of the hyphen 40 (This should represent an arbitrarily large interim time interval for the sections A, C and D) Fuel pressure curve value series 35 respectively. 36 represented, which were determined for two different operating points. The fuel pressure value series 35 respectively. 36 each consist of time-discrete measured values of the pressure sensor (in 1 with the reference number 18 provided) in the low-pressure fuel system, the high frequency over a total measuring time interval t1 and t2 in the time frame t (with t << t1 and t << t2) or with the frequency 1 / t are determined.

In 2 is to the right of the hyphen 40 in section C and section D shows how the driving time of the injector for the different operating points is determined according to the presented method. For the first operating point present in section C, the fuel pressure curve value series assigned to this operating point is determined 35 determines that the control or opening of the injection valve during a pressure wave 37 the fuel pressure will occur. In order to inject a predetermined amount of fuel despite the lower fuel pressure, therefore, the driving time (represented by bars 31 ) extended to TE1> TE. For the present in section D second operating point is based on the operating point associated fuel pressure curve value series 36 determines that the control or opening of the injection valve during a pressure wave peak 38 the fuel pressure will occur. In order to inject a predetermined amount of fuel despite the increased fuel pressure, therefore, the driving time (represented by bars 32 ) to TE2 <TE.

When measured in the fuel low pressure system pressure fluctuations have a characteristic of a particular sinusoidal pressure wave, as exemplified in 2 2, a respective fuel pressure history value series may be represented in value by the time period required for detecting a full period of the pressure wave (with reference to FIG 2 : t1 or t2) or by a frequency formed by the reciprocal of the period (with reference to 2 : 1 / t1 or 1 / t2), the amplitude of the pressure wave (with reference to 2 : A1 or A2) and a referenced phase (in 2 show the curves 35 and 36 a phase difference of 180 degrees to each other) can be specified.

Claims (15)

Method for controlling a port injection of a fuel injection system of an internal combustion engine with a port injection system and a direct injection system with a common low-pressure fuel system, wherein an injection valve ( 13 ) of the intake manifold injection system during a determined actuation duration of the injection valve ( 13 ) is driven for the purpose of fuel intake manifold injection of a predetermined amount of fuel, characterized in that during a current operating point of the internal combustion engine and the fuel injection system, the drive duration (TE1, TE2) of the injection valve ( 13 ) is determined on the basis of a fuel pressure curve that has been previously measured in operating mode specifically and assigned to the current operating point. A method according to claim 1, characterized in that a respective fuel pressure course value series ( 35 . 36 ) by means of high-frequency ( 1 / t) Measurement of fuel pressure fluctuations caused by operating the intake manifold injection system and / or the direct injection system with a pressure sensor arranged in the low-pressure fuel system ( 18 ) has been determined. A method according to claim 2, characterized in that a respective fuel pressure gradient value series ( 35 . 36 ) specifies the measured fuel pressure fluctuations as a fuel pressure wave, the fuel pressure history value series being represented by a frequency ( 1 / T1, 1 / t2), a phase and an amplitude (A1, A2) or damping of the fuel pressure wave is specified in terms of value. Method according to one of the preceding claims, characterized in that each operating point of the internal combustion engine and of the fuel injection system used for determining the activation duration, to which a respective unique operating point specifying data set is assigned, by a rotational speed and a torque of the internal combustion engine and at least one determined operating parameter value of the fuel injection system the group of a temperature of the fuel in the low-pressure fuel system, a viscosity of the fuel, a compression modulus of the fuel and a combustion property of the fuel is specified. Method according to one of the preceding claims, characterized in that the determination of the actuation duration (TE1, TE2) on the basis of a previously determined in engine operation operating point specific association between a plurality of measured in the low-pressure fuel pressure curve value series and a plurality of operating point-specifying data sets. A method according to claim 5, characterized in that the assignment during operation of the fuel injection system provided with the internal combustion engine is determined by a learning method. A method according to claim 6, characterized in that the allocation is updated at predetermined time intervals by means of a weighted and / or filtered learning, and that a fault is detected in the low-pressure fuel system if an extent of updating the allocation exceeds a predetermined threshold. Method according to one of claims 6 or 7, characterized in that the learning or updating of the assignment in a first operating phase type of the internal combustion engine with inactive intake manifold injection and active direct injection and / or in a second operating phase type of the internal combustion engine with active intake manifold injection and inactive direct injection takes place or alternatively the first and second operating phase type in a third operating phase type of the internal combustion engine with active intake manifold injection and active direct injection takes place. Method according to one of claims 5 to 8, characterized in that the assignment is stored as a table in a memory or by training a numerical model. Method according to one of claims 5 to 9, characterized in that based on the assignment, a time interval for the control of the injection valve is determined for the based on the assignment of an increased fuel pressure or fuel pressure wave mountain ( 38 ) is predicted in the common low-pressure fuel system. Method according to one of the preceding claims, characterized in that the control duration (TE1, TE2) of the injection valve by a predetermined reference value (TE) and a correction value for taking into account fuel pressure fluctuations in the common low-pressure fuel system is determined, the correction value based on the previously in Engine operating point-specific measured and the current operating point associated fuel pressure curve is determined. Method according to one of the preceding claims, characterized in that for a plurality of injection valves of the intake manifold injection system whose respective Ansteuerdauern for an identical operating point of the internal combustion engine and the fuel injection system based on the previously operating point specific measured in the engine operating point and the identical operating point associated fuel pressure curve are determined individually. An electronic control device adapted to carry out one of the methods of any preceding claim. A computer program comprising computer processable instructions for performing one of the methods of any one of claims 1 to 12. A machine-readable storage medium having a computer program stored thereon according to claim 14.

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