CN106837578B

CN106837578B - Fuel distribution for internal combustion engine operation

Info

Publication number: CN106837578B
Application number: CN201611109456.7A
Authority: CN
Inventors: R.埃克; T.库恩; T.霍尔曼; U.舒尔茨
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-12-07
Filing date: 2016-12-06
Publication date: 2022-12-20
Anticipated expiration: 2036-12-06
Also published as: DE102015224409A1; CN106837578A

Abstract

The invention relates to optimizing fuel distribution for the operation of an internal combustion engine having a plurality of cylinders (64), wherein direct injection and intake manifold injection are provided for fuel distribution, and provides that during operation of the internal combustion engine, a fuel portion distributed by direct injection and a fuel portion distributed by intake manifold injection are determined individually for at least one cylinder (64) and fuel is distributed according to an injection strategy (61) known in this way.

Description

Fuel distribution for internal combustion engine operation

Technical Field

The invention relates to a fuel distribution method for operating an internal combustion engine having a plurality of cylinders and to a corresponding fuel distribution system.

Background

The operation of an internal combustion engine with intake pipe injection and direct gasoline injection makes it possible to use both injection methods for the corresponding advantages of an optimal mixture formation and the resulting combustion, and furthermore, in this way a reduction in fuel consumption is achieved. In particular, at full load and with increasing dynamics of the internal combustion engine, gasoline direct injection systems are more advantageous, since the tendency to knock is less here. In contrast, intake manifold injection is more advantageous in the case of part load, since the amount of particles, in particular soot particles, and the amount of hydrocarbons produced during combustion is lower here.

The injection strategy used for optimal mixture formation and combustion is understood to be an injection strategy that can be Direct Injection (DI), port injection (PFI) or a combination thereof (DI-PFI split operation). The injection strategy according to the state of the art is based on the most critical or critical (kricischsten) cylinder for the respective operating point of the internal combustion engine. This means that the injection strategy provides space for optimization.

Disclosure of Invention

The aim of the invention is to optimize the operation of an internal combustion engine having a DI system and a PFI system with regard to costs and exhaust emissions.

This object is achieved by the method mentioned at the outset in that during operation of the internal combustion engine, for at least one cylinder, the fuel portion distributed by direct injection and the fuel portion distributed by intake manifold injection are determined individually (individuell) and the fuel is distributed according to the injection strategy thus determined. Preferably, the injection strategy is determined individually for each cylinder.

According to the invention, the injection strategy is therefore no longer determined for the entire motor but for the cylinders individually. This means in particular that the DI-PFI split operation is no longer determined for the entire motor in the cylinder-generic manner, but a split factor is known for each cylinder individually. Furthermore, operation of individual cylinders in DI-mode and other cylinders in PFI-mode may be achieved.

The invention has the advantage, in particular, of extending the operating range of the intake pipe injection, which is limited in part by the susceptibility to knocking or the combustion stability of the individual cylinders, which makes possible a further optimization of the motor with regard to costs and exhaust emissions.

According to one possible embodiment of the invention, the optimum operation of the injection path for each cylinder is stored in a corresponding characteristic field, by means of which the injection strategy is known individually for the cylinder. This is preferably carried out in dependence on operating parameters of the motor, such as motor speed, motor load, intake air temperature, motor temperature, operating mode (continuous operation, shift operation, intermediate operation), AGR-rate, valve control times, valve control curves, fuel type (e.g. octane number and/or alcohol content). Depending on the availability, the accuracy of the effort and the expected effort, different combinations of the aforementioned operating parameters can be taken into account for the knowledge of the injection strategy of the individual cylinders.

With the method according to the invention or the device according to the invention, a switching of the overheated cylinder to the direct injection can be carried out or the DI part can be increased in the event of thermal problems of the motor in the outer region, for example caused by differences in the installation location or the intake air temperature. In this way, due to the removal of heat from the evaporated fuel, a stronger cooling of the cylinder interior is produced directly in the cylinder, so that the knocking tendency is decisively reduced by the partial increase of the DI injection quantity.

In order to prevent knocking during knock control, a hysteresis adjustment of the ignition angle is currently performed (Sp 228tverstellung). The further the ignition angle is adjusted in the direction of the retardation, the further the combustion center of gravity position is and the less the tendency for knocking.

According to a further development of the invention, the cylinders are individually matched and the division factor is shifted in the direction of the direct gasoline injection in order to reduce the knocking tendency in this way. In this way, at least for individual cylinders, a return of the firing angle reserve (Zur ü cknahme), i.e. a distance of the selected firing angle from the optimum firing angle for the cylinder in which combustion occurs at the knock limit, is possible. In this way, a further cost advantage can be achieved. According to one possible embodiment, the knock control takes place on two paths: fast interference through firing angle adjustment and slower interference through splitting coefficients and partial return of firing angle (ruckfuhren).

According to one particularly advantageous embodiment, the knock interference and the resulting change in the division factor are learned and an optimal injection strategy is adapted (adaptive) for each motor sample. The basic application of the motor can thus be supported by the so-called optimal case and it is not necessary for the PFI to restrict the operating range to the so-called worst case behavior of the individual cylinders again.

One possible implementation of the adaptation can be carried out as a special operation by means of a targeted adaptation mode. In this case, for example, all cylinders are operated in the pure DI mode at an operating point with respect to the knock threshold (kricischen). In this case, it is optionally possible to carry out a targeted adjustment of the ignition angle in order to achieve a critical operating point with respect to knocking. In the next step, the change of the split coefficient in the direction of the intake pipe injection (PFI) is performed for the selected cylinder until knocking combustion can be determined. The split coefficient is then saved for that cylinder. Preferably, the saving is performed in relation to the operating point. Thereafter, the method is performed for the other cylinders. Thus, knock regulation can be optimized individually for each cylinder.

Alternatively, provision can be made here for the adaptation mode to be started in pure PFI operation. In the critical operating point, the ignition angle for the cylinder is adjusted in such a way that knocking occurs precisely. The DI-fraction is then increased until knocking combustion no longer occurs. The interference of the firing angle and the division factor is advantageous here, since the firing angle and the division factor should be adjusted alternately in the "advance" direction and in the "DI" direction in order to obtain the optimum parameters.

Furthermore, it is advantageous for the determination of the injection strategy for individual cylinders to include one or more of the following variables, relationships and/or characteristics:

a wall film model for calculating and/or correcting the wall film flow (wandfilmfluusses), not only for the intake pipe but also for the combustion chamber;

the correlation of the calculation of the individual firing cylinders with the selected injection, i.e. for example the current splitting factor;

-heat engine operating factors (warlauffaktor);

a torque model for correcting a torque difference which is obtained by a firing angle interference and/or a valve lift interference (ventilhubeningriffe) of the individual cylinders.

Further features, application possibilities and advantages of the invention emerge from the following description of exemplary embodiments, which are illustrated by means of the drawings, wherein these features may be important for the invention not only in individual cases but also in various combinations and are therefore not specified in any detail.

Drawings

FIG. 1 shows a simplified schematic representation of a vehicle having an internal combustion engine which can be operated by means of direct gasoline injection and intake manifold injection and which is operated with gasoline injection and intake manifold injection

FIG. 2 illustrates a block diagram in which several functional blocks of one possible embodiment of the present invention are shown;

FIG. 3 shows a flow chart comprising steps that may be taken in performing an adaptation according to a further possible embodiment; and is

Fig. 4 shows a further flowchart comprising possible steps in performing the adaptation according to a further possible embodiment.

Detailed Description

Fig. 1 schematically shows a vehicle 1, which comprises an internal combustion engine 2 for operating the vehicle 1. A control unit 3 is arranged in the vehicle 1, which control unit makes possible the control and/or regulation of the internal combustion engine 2 and in particular the control of the mixture formation. The internal combustion engine 2 has cylinders 4. At least one direct injection valve 5 is associated with each cylinder 4. Each direct injection valve 5 is connected to the controller 3 via a signal line 6.

The direct injection valve 5 is connected via a high-pressure accumulator 7 (high-pressure rail) to a high-pressure fuel pump 8. The high-pressure fuel pump 8 is connected to the controller 3 via a data line 9.

Fig. 1 also shows a fuel tank 10, which is equipped with a low-pressure fuel pump 11. The low-pressure fuel pump 11 is connected to the controller 3 via a data line 12.

The fuel delivered by the low-pressure fuel pump 11 from the fuel tank 10 reaches the high-pressure fuel pump 8, which generates the pressure necessary for the direct injection of gasoline, via a low-pressure fuel line 13. Furthermore, in the exemplary embodiment shown in fig. 1, the low-pressure fuel pump 11 supplies the pressure required for the intake manifold injection. In this case, the fuel reaches a low-pressure fuel accumulator 15 (low-pressure fuel rail) via a low-pressure fuel line 13. The low-pressure fuel accumulator 15 is connected to an intake manifold injection valve 16 (PFI valve).

The controller 3 has a processor 22 and a memory element 23. In the memory element 23, for example, a computer program 24 is stored which is programmed for carrying out the method according to the invention. The method according to the invention is then carried out by means of the controller 3 when the computer program 24 is run on the processor 22.

The internal combustion engine 2 is connected to an exhaust gas system 25, which comprises an exhaust gas catalytic converter 26 and a lambda probe 27. The internal combustion engine 2 is provided with a knock sensor 28.

Fig. 2 shows a block diagram in which several components are shown, which can be used according to a possible embodiment of the invention. The block diagram begins with an example in which the engine includes four cylinders 64. An injection strategy 61 is known for each cylinder 64, wherein the injection strategy 61 comprises, in particular, a division factor which specifies the portion of the fuel which is distributed by the intake manifold injection 62 and the portion of the fuel which is distributed by the gasoline direct injection 63. The splitting factor is known in relation to a characteristic field 60, wherein, according to a preferred embodiment, the characteristic field 60 is determined individually for each cylinder 64. In order to determine the injection strategy 61 and thus in particular the division factor by means of the characteristic field 60, a plurality of characteristics and input variables 50 are taken into account. The characteristic and input variables 50 include, in particular, operating parameters 51, which themselves include, for example, motor speed, motor load, intake air temperature, operating mode (continuous operation, shift operation, intermediate operating mode with split injection), AGR rate, valve control times, valve control curves and the current fuel type or fuel properties, such as octane number and alcohol content.

Furthermore, in the block diagram shown in fig. 2, a wall film model 52 for calculating and correcting the wall film flow is taken into account not only in the intake manifold but also in the combustion chamber. Furthermore, taking into account the thermal engine operating factors 53 and providing a torque model 54, by means of which a correction of the torque difference is possible by means of a suitable ignition angle intervention or a valve lift intervention of the individual cylinders.

In addition, characteristic and input variables 50 include a block 55, in which the calculation of the individual cylinders firing is typically carried out, which is dependent on the current injection, in particular also on the division factor. Thus, ignition is calculated for each cylinder individually by means of the function block 55.

It goes without saying that a plurality of interactions, which are not shown in fig. 2, are possible and can advantageously be realized. For example, the division factor determined by means of the characteristic field 60 may itself take into account the characteristics and the input variables 50 and/or indirectly and/or directly in the determination of further division factors or injection strategies, so that the values determined in relation to the characteristic field 60 may be taken into account in the determination of the injection strategies for the respective further cylinders.

Fig. 3 shows a flowchart in which several method steps are shown, which are carried out according to one possible embodiment in order to learn the knock interference and the resulting change in the division factor during a specific operation of the internal combustion engine, for example in a targeted adaptation mode, and to adapt the optimal operating strategy for each motor sample.

The method starts with step 100 in which an adaptation mode is initiated. In step 101, all cylinders are operated in the pure DI mode, so that fuel is completely or approximately completely dispensed by direct gasoline injection. In step 102, a cylinder is selected and in step 103 the splitting factor is shifted in the direction of the intake manifold injection. In step 104, it is checked, for example by means of the knock sensor 28, whether knocking of the combustion can be determined. If this is not the case, the splitting factor continues to be shifted in the direction of the intake pipe injection. Otherwise, the split coefficients are saved with other operating parameters in step 105.

In step 106 it is checked whether an adaptation has been performed for all cylinders. If this is not the case, the next cylinder is selected in step 102 and the method is re-executed for that cylinder. If the split coefficients are saved for all cylinders, the method ends in step 107.

Another possible implementation of the method is shown in fig. 4. Starting from step 200, an adaptation as a special run is initiated. In step 201, the internal combustion engine is operated in a pure or nearly complete PFI mode, so that fuel is dispensed predominantly or exclusively by intake manifold injection. In step 202, a cylinder is selected and in step 203 the ignition angle for this cylinder is adjusted in such a way that knocking occurs. In step 204, the DI-fraction of the fuel dispensed is increased until detonation combustion no longer occurs. At the same time, in step 205 the ignition angle is adapted and in step 206 it is checked whether knocking occurred. Once knocking occurs, the division factor is shifted in the direction of Di in

steps

204 and 205 and the ignition angle is adapted accordingly. When knocking no longer occurs, the split coefficient is saved in step 207. In addition, the firing angle and other operating parameters are saved or the characteristic field 60 is updated.

In step 208 it is checked whether the adaptation is performed for all cylinders. If this is not the case, then the next cylinder is selected in step 202. Otherwise, the method ends in step 209.

It is self-evident that the method steps shown in fig. 3 and 4 are exemplary to be understood as suitable possible embodiments and are used primarily to explain the invention.

Claims

1. Fuel distribution method for operating an internal combustion engine (2) having a plurality of cylinders (4), wherein a direct injection and an intake manifold injection are provided for fuel distribution, characterized in that a fuel fraction distributed by a direct injection and a fuel fraction distributed by an intake manifold injection are determined individually for at least one cylinder (4) during the operation of the internal combustion engine (2) and the fuel is distributed according to an injection strategy (61) known in this way, wherein knock interference and a change in the resulting splitting factor are learned in a special operation of the internal combustion engine (2) in an adaptation mode (100,

in the adaptation mode (100

-first of all, for at least one cylinder (4), the fuel is distributed by direct injection in such a way that a critical operating point exists with respect to knocking;

-performing a change of the split coefficient towards the intake pipe injection direction for the fuel distribution for that cylinder;

checking whether knocking occurred, if this is not the case, continuing to shift the splitting factor in the direction of intake pipe injection, otherwise saving it together with other operating parameters,

or

In the adaptation mode (100

-first of all fuel is distributed at least for one cylinder (4) by intake pipe injection;

-adjusting the ignition angle for the cylinder (4) such that knocking occurs;

-performing a change of the split coefficient in the direction of direct injection and performing a further adjustment of the ignition angle for the fuel distribution for that cylinder (4);

checking whether knocking still occurs, if this is the case, continuing to shift the division factor in the direction of the direct injection and correspondingly matching the ignition angle, if knocking no longer occurs, saving the division factor together with the ignition angle and other operating parameters.

2. Method according to claim 1, characterized in that the injection strategy (61) is determined individually for each cylinder (4).

3. A method according to claim 1 or 2, characterized in that the injection strategy for individual cylinders is determined in relation to current operating parameters (51) of the internal combustion engine (2).

4. Method according to claim 3, characterized in that at least one of the following operating parameters (51) is taken into account for the determination of the injection strategy (61):

-number of motor revolutions;

-a motor load;

-an intake air temperature;

-motor temperature;

-a mode of operation;

-an AGR rate;

-a valve control time;

-a valve control curve;

-the fuel type.

5. Method according to claim 1 or 2, characterized in that the ignition angle is adapted in relation to the current injection strategy (61) of at least one cylinder (4) for achieving an optimum operation of the internal combustion engine (2) in terms of knock control.

6. Method according to claim 5, characterized in that the internal combustion engine is operated in the adaptation mode (100.

7. Method according to claim 1 or 2, characterized in that in the determination of the injection strategy (61) for individual cylinders at least one of the following variables is taken into account:

-a wall membrane model (52) for calculating and correcting the wall membrane flux;

-a current ignition (55) associated with a current injection strategy (61);

-heat engine operating factors (53);

-a torque model (54) for correcting for differences in torque.

8. Fuel distribution system for an internal combustion engine (2) having a plurality of cylinders (4), wherein direct injection and intake pipe injection are provided for fuel distribution, characterized in that the fuel distribution system has means for carrying out the method according to one of claims 1 to 7.

9. Controller (3) for controlling and/or regulating the operation of an internal combustion engine (2), characterized in that the controller (3) is programmed for performing the method according to any one of claims 1 to 7.

10. A controller (3) according to claim 9, characterized in that the controller (3) is adapted to control and/or regulate the fuel distribution system.

11. Storage element (23) on which a computer program (24) is stored, which computer program can be run on a controller (3) for controlling and/or regulating the operation of the internal combustion engine (2), characterized in that the computer program (24) is programmed for carrying out the method according to one of claims 1 to 7 when the computer program is run on the controller (3), wherein the storage element (23) is implemented as a storage area corresponding to the controller (3), as a random access memory, as a read-only memory, as an optical storage medium or as a virtual memory.

12. A storage element (23) according to claim 11, wherein the computer program is executable on the controller (3) for controlling and/or regulating the fuel distribution system.