EP1190167B1 - Method and device for operating an internal combustion engine with direct gas injection - Google Patents

Description

State of the art

The invention relates to a method and a device for operating an internal combustion engine with gasoline direct injection.

EP 0 838 582 already discloses a method for controlling the intake of a four-stroke engine known with direct injection gasoline, in which two cylinders or groups different from cylinder through a different inlet of air and fuel work. One cylinder group works with a rich mixture and the other with a skinny one. To reduce the pollutant emission is a part of the exhaust gas of the fat-operated cylinder group is recirculated to an inlet common to all cylinders.

A method and apparatus for operating an internal combustion engine with gasoline direct injection is also described in DE 43 32 171 A1 (US Patent 5,483,934). In which Control system shown there is the entire operating range of the internal combustion engine after Speed and load divided into different areas and depending on the current operating range the fuel is injected either during the intake stroke or during the compression stroke. Injection during the intake stroke is due to the available standing time to ignition and due to the swirling of the injected Fuel through the intake air flow a largely homogeneous fuel distribution (Homogeneous operation), while in the case of injection in the compression stroke a stratified charge arises (shift operation). In homogeneous operation, the internal combustion engine is operated throttled, i.e. the air supply is limited by a throttle valve, in stratified charge mode almost unthrottled operated throttled, i. the air supply through the throttle almost unlimited. Between these modes depends on the mentioned operating variables and / or of other predetermined criteria, e.g. in terms of performance requirements by the driver, switched.

It is an object of the invention to operate an internal combustion engine with gasoline direct injection to further optimize.

This is due to the distinctive features of the independent Achieved claims.

Advantages of the invention

In the above-mentioned prior art is between the individual operating modes of the internal combustion engine always for the switched over entire internal combustion engine. Furthermore, all wear Cylinder evenly to the torque of the internal combustion engine at. Thus, flexibility and degrees of freedom in the Design of the controller given away.

By an asymmetric operation of an internal combustion engine with gasoline direct injection, especially when the internal combustion engine at least two independently controllable Cylinder banks, will be another optimization reaches the drive of a motor vehicle.

Of particular advantage is that in operating states in which not by the low-consumption stratified charge operation more the driver's desired performance is provided can, only a part of the internal combustion engine, for example a cylinder bank, in comparison, consumption-intensive Homogenous operation is operated. The other cylinder bank continues with the low-consumption stratified charge mode operated. Thus, on the one hand, the increased Power requirement of the driver to be provided On the other hand, the consumption can be minimized. This advantage is achieved by the fact that the contribution of individual Cylinder banks or groups different to the total moment is given.

Another advantage of such asymmetric operation the internal combustion engine is achieved, is an improvement the noise emission or, more generally, the comfort of the Internal combustion engine. Particularly advantageous in this context, that when clearing a storage catalyst in Idle or in the partial load range, not all banks at the same time be switched. By switching alternately the noise emission is optimized.

Of particular importance is that by the asymmetric Operation of the internal combustion engine with gasoline direct injection more degrees of freedom in the design of the exhaust gas concepts be available. For example, the power request becomes the driver implemented so that a part the internal combustion engine in an exhaust gas-optimal mode and operated at an exhaust gas-optimal operating point, while the actual power requirement of the driver by controlling the operating point and possibly the Operating mode of another part of the internal combustion engine is carried out.

Of particular advantage is the application of the asymmetric Operating in an internal combustion engine with gasoline direct injection, the at least two cylinder banks with at least Has two independently controllable throttle. Advantageously, however, this idea can be even with internal combustion engines with only one throttle apply, with the air filling is adjusted so that a part of the cylinders of the internal combustion engine is homogeneous, the other is operated in a stratified mode. The latter leads to an overall increased air charge, so that the throttle losses compared to a homogeneous operation of the entire Internal combustion engine are reduced.

In addition to switching between the modes with Stratified charge and with homogeneous fuel mixture formation becomes the principle of asymmetric operation of the internal combustion engine also between operating modes such as homogeneous stoichiometry, homogeneous-lean or mixed modes such as a double injection mode in which both homogeneous as well as stratified fuel mixture arises, applied. Again, the asymmetric ones Operation achieved advantages as shown above achieved.

Further advantages will become apparent from the following description of embodiments or of the dependent Claims.

drawing

The invention will be described below with reference to the drawing illustrated embodiments illustrated. FIG. 1 shows an overview diagram of a control device for Control of an internal combustion engine with gasoline direct injection. In Figure 2 is based on an embodiment of a Flowchart illustrating the principle of asymmetric Represents operation of such an internal combustion engine. Finally, FIG. 3 shows a further exemplary embodiment which is a preferred embodiment outlined as a flow chart.

Description of exemplary embodiments

FIG. 1 shows a block diagram of a control device for controlling an internal combustion engine with gasoline direct injection. It is a control unit 10 is provided which as Components an input circuit 14 at least one microcomputer 16 and an output circuit 18. One Communication system 20 connects these components to each other Data exchange. The input circuit 14 of Control unit 10 are supplied to input lines 22 to 26, which in a preferred embodiment as Bus system are executed and via the the control unit 10th Supply signals which are used to control the internal combustion engine represent operating variables to be evaluated. These signals are detected by measuring devices 28 to 32. such Operating variables are accelerator pedal position, engine speed, engine load (e.g., air mass), exhaust gas composition, engine temperature, etc. About the output circuit 18 controls the controller 10 the performance of the internal combustion engine with gasoline direct injection. This is shown in FIG. 1 on the basis of the output lines 34, 36 and 38 symbolizes which at least the fuel mass to be injected, the ignition angle of the internal combustion engine and at least one electrically operable Throttle valve for adjusting the air supply to the internal combustion engine actuate. The representation chosen in FIG. 1 means in that on the symbolic output line 34th the injectors of a certain number of cylinders the internal combustion engine are actuated, i. the injected Fuel mass is supplied to these cylinders, over the output line 36 of the spark in these cylinders to predetermined time is triggered and an electric Actuatable throttle is controlled, which controls the air supply affected to these cylinders.

In internal combustion engines with at least two cylinder banks or groups in which each cylinder bank has an electric controllable throttle the air is supplied In essence, two versions are provided in Figure 1 are shown by dashed lines. For one thing, the second cylinder bank, there at least the injected Fuel mass, the ignition angle and the air supply, analog to the first cylinder bank via the output circuit 18 as well Output lines 34a, 36a and 38a, the output lines 34, 36 and 38 are controlled by the controller 10. That is, a controller controls at least two Cylinder banks. In another embodiment is instead of lines 34a to 38a, a second controller 10b provided, which is constructed analogously to the control unit 10 and which via the output lines 34b, 36b and 38b Fuel mass, ignition angle and air supply at least one another cylinder bank sets. The two control units 10 and 10b are via a communication system connecting them 40 for mutual exchange of data with each other. At least one person will be able to use this communication system the control units depending on the embodiment individual or all of the other detected magnitude data signals or from these derived operating variables for further Evaluation transmitted. In another embodiment Input lines 22b to 26b are next to the controller 10 also supplied to the control unit 10b, so that there alternatively for transmission over the communication system or in addition the operating variable signal is directly available.

The basic procedure for those in the microcomputer 16 of the control unit 10 running control of the internal combustion engine is sketched with reference to the flowchart of Figure 2. As essential operating variables are the microcomputer 16 the accelerator pedal position β and operating variables such as engine speed NMOT, air mass MHFM and set torques of others Control systems, for example, by a traction control system and / or a transmission control supplied. In the driver request pictures 100 is from the supplied accelerator pedal position signal β at least taking into account the engine speed, optionally a correction variable of an idle speed control, etc., a driver's request moment MIFA the Internal combustion engine determined. This is done in the preferred Embodiment by means of a map and the following Calculation steps. Further, the microcomputer 10 Desired torques of other control systems, e.g. a desired moment of a Drive slip control MIASR, a transmission control MIGS, etc. supplied. These desired torques and the driver's desired torque are fed to a selection stage 102, in which from the supplied Set torques a resulting desired torque MISOLL For controlling the internal combustion engine is determined. In the preferred Embodiment, the selection is made by minimum or maximum selection. The determined in this way resulting target torque MISOLL becomes another coordinator 104 supplied, in which the following with reference to Flowchart of Figure 3 described specifications for a asymmetric operation of the internal combustion engine can be determined. The coordinator 104 sets the total target torque MISOLL in individual rolling moments MISOLL1 to MISOLLN for the individual Cylinder banks or for individual cylinder groups and / or in Desired modes BASOLL1 to BASOLLN of the individual cylinder banks or cylinder groups. The division of the target torque and the specification of desired modes by the Coordinator 104 takes place according to predetermined strategies.

In normal operation at low and medium loads all cylinder banks or all cylinder groups for consumption reasons operated in stratified charge mode. Normally The set torques are evenly applied to the individual benches divided up. Is the target torque MISOLL an increased power requirement recognized by the engine, not only by provided a stratified charge operation of all cylinder banks can be, the target torque for one of the cylinder banks or the cylinder groups increases, whereupon these optionally the mode changes and / or their desired mode set to homogeneous operation. This will be in the Compared to a complete switchover a consumption optimization achieved because the other cylinder banks or Cylinder groups still in the consumption-optimal, lean Stratified charge operation are operated. The same applies for the other modes, such as a lean operation with homogeneous mixture formation or mixed modes with double injection, in which both homogeneous as well as layered fuel mixture formation takes place. Also here will be in the presence of an increased power requirement individual cylinder banks or groups as far as possible in the operated more fuel-efficient operation and another bank or group to provide the moment in a performance-optimized Switched operating mode.

Another strategy used in coordinator 104 in one embodiment implemented is a comfort optimization, after the switching of individual cylinder banks or Cylinder groups never change from one mode to another simultaneously but temporally one after the other. Thereby, the noise emission associated with the switching becomes reduced.

Especially in storage catalytic converters must to clear the Catalyst from time to time from stratified charge operation in To switch the operation with homogeneous mixture formation. Also in this context, the illustrated Procedure of the asymmetric operation of the internal combustion engine use successfully, since at least idle and Part load range both banks not switched at the same time must be to clear the catalyst, but in succession can be switched or with only one catalyst for all banks or cylinder groups only the alternating switching of a cylinder bank or cylinder group sufficient. This is a significant comfort improvement, in particular a reduction of the noise emission be achieved.

In a particularly advantageous manner, in addition to a consumption-based and a comfort-optimal strategy also an exhaust gas-optimal Strategy (e.g., in the area of low power requirements) be used. The division takes place the torques and / or the specification of the desired mode such that the lowest possible exhaust pollution occurs. It is thus e.g. tries the total target torque as long by lean operation in the shift and / or homogeneous operation ready as long as with the respective operating mode this moment is adjustable. Only then is at a cylinder bank or group by specifying a different one Sollmoments and / or a desired mode a less exhaust gas optimal Operating point set.

The individual desired torques MISOLL1 to MISOLLN and the corresponding Desired modes become the respective control signal images 106 to 108 for the individual cylinder banks or cylinder groups supplied, in which, taking into account of operating variables such as engine speed, relative air charge (derived from the supplied air mass), etc. the respective nominal torque taking into account the desired Operating mode in a fuel mass to be injected, a Ignition angle and a throttle position can be implemented. It may happen that the desired mode is not can be met, for example, when a runflat situation present, with no adjustability of the Nominal torque, with special operating functions such as start, warm-up, Katheizen, etc.

FIG. 2 shows a system in which for each Cylinder bank or group can control its own throttle is. In this case, the mode of operation for each bank are freely chosen and the torque requirements so on the Banks are distributed, that is optimal efficiency the internal combustion engine or depending on the strategy an optimal Operation of the internal combustion engine results. Owns the internal combustion engine only one throttle, so this is so adjust that results in an air filling, it by appropriate calculation of the fuel mass allowed, a Cylinder bank homogeneous and another cylinder bank layered to operate. This is one over the homogeneous Operation of the internal combustion engine as a whole increased air charge adjusted, which throttle losses are reduced. A quick change of the operating mode of the cylinder banks by controlling the fuel mass is possible here.

An embodiment of the coordinator 104 is based on the Flowchart of Figure 3 the example of an internal combustion engine with two independently controllable cylinder banks or - groups outlined in more detail. The program is given in Go through time intervals.

In the first program step 200, the total desired torque MISOLL detected. In the next step 202 will be on the Based on this target torque checks if an increased power requirement is present. In a preferred embodiment this is the case when the nominal torque exceeds a predetermined limit. This threshold is sized so that it is approximately a borderline corresponds, above which the internal combustion engine with homogeneous Mixture be operated for performance reasons would. Has been in step 202 an increased power requirement detected, it is checked in step 204 whether the power request is so high that all cylinder banks or switch groups. This is the case when a desired torque value is required, which is close to the maximum value lies. If this is the case, according to step 206 initially as the desired mode of the first bank or cylinder group BASOLL1 the homogeneous mode output and a Setpoint torque value MISOLL1 for this cylinder bank or group determined. This setpoint torque value is in a preferred Exemplary embodiment based on the total nominal torque value, which is read in step 200 formed. Especially is a percentage of this nominal torque value> 50% specified. Thereafter, in step 208, based on a If necessary, the notified mark checks whether the switchover finished. If this is the case, it will be in step 210 also for the second cylinder bank or cylinder group as Desired mode of homogeneous operation output and the Target torque of this cylinder bank or group on the basis the Gesamttsollmoments and the desired torque of the first cylinder bank or group determined. Is the switchover the first Cylinder bank according to step 208 is not yet finished, is in step 212, the desired mode of operation of the second cylinder bank recorded on stratified charge mode and as desired torque value according to step 210, the difference between the total desired torque value and the desired torque value of the first Bank determined. After steps 210 and 212, in the Step 214 outputs the formed setpoints and if no higher-level specifications, e.g. Emergency operation, missing Feasibility of the setpoint torque value in the desired operating mode, etc., realized. After that, the program part finished and again at the next time interval run through.

If, according to step 204, a power request has been detected, which does not require switching of all banks is according to Step 216, the target mode of a bank on the homogeneous operation, that of the other bank on the stratified charge operation set. Likewise, the target moment of a bank, the is to be operated homogeneously, formed analogously to step 206, while the target moment of the other bank, in the Stratified charge operation, based on the total desired torque and the target torque of the first bank becomes. This is followed by step 214. By the steps described in step 216 asymmetric operation of the internal combustion engine becomes a consumption-optimal control of the internal combustion engine achieved with increased performance requirement, as a Part of the internal combustion engine continues in fuel-efficient Stratified charge operation is operated. Likewise, a comfort improvement achieved because the benches or groups one after the other, can not be switched at the same time. The mentioned Strategies, in addition to the subsequent switching for catalyst removal and exhaust-optimized control comes, depending on the design all together or in any combination, also used individually.

If there is no increased power demand according to step 202 before, in step 226 it is checked whether the conditions for Clearing a storage catalyst present. Are the conditions cleared for, is in step 228 for a cylinder bank as a desired mode of homogeneous operation output and a corresponding desired torque (for example, minimum desired torque for this operating mode). In the following Step 230 is called the other bank's desired mode furthermore, the stratified charge mode is output and the setpoint torque based on the total desired torque and the desired torque the first bank. This is followed by step 214. By this measure, a clearing of the storage catalyst achieved without the entire internal combustion engine in to switch the homogeneous operation is. Thus, in addition to consumption also achieved noise and thus comfort improvements.

Are the conditions for clearing the catalyst not before, in step 218, the target mode of the first bank on stratified charge mode and a corresponding one Target torque determined from the setpoint torque value specified. This corresponds in a preferred embodiment 50% of the total setpoint torque value read in step 200. In the next step 220 becomes checks, if necessary, the switchover from shift to Homogenous operation is completed. If this is the case, it will Step 222 also the second cylinder bank to the desired mode Layer charge set and the corresponding Setpoint based on the total setpoint torque value and the setpoint torque value of the first bank formed. Is the switch not completed in step 220, i. is the system becomes the second bank in step 224 as previously controlled and the setpoint torque value formed analogous to step 222. By this measure prevents both banks from switching simultaneously and in this way loss of comfort. After that follows Step 214.

In a preferred embodiment is provided in asymmetric operation of the internal combustion engine, i. during operation the internal combustion engine with two different modes or with two different nominal torque values, the respective operating state of the cylinder banks of To alternately change the internal combustion engine, i. in one predetermined time grid, for example, during operation of the one Cylinder bank in homogeneous and the other in shift operation to switch the banks so that the first bank in the Shift and the second bank operated in homogeneous operation will (toggle).

In the described embodiment, two cylinder banks provided, which via two independently controllable electrically operated throttle valves. Next Such a solution is the solution according to the invention also on internal combustion engines with several cylinder banks and several (according to the number of cylinder banks) independently mutually controllable throttle valves, in particular also to be used on engines with individual throttle valves for each cylinder.

In another embodiment, at least in certain Operating situations, e.g. at high torque and Performance requirements, the cylinder banks switched simultaneously. This will improve the dynamic Behavior achieved. Based on the program in Figure 3 means this that the steps 208 and 212 and possibly the Steps 220 and 224 at least in said operating state omitted and steps 206 and 210 and the steps 218 and 222 summarized.

In general, a cylinder bank or group is then switched, when the first cylinder in the new mode is operated. At the same time, therefore, the meaning of that switching to a bank or group within a period of time is introduced between the Switching signal and the successful injection in the first cylinder in the new mode at the bank or group is where the operating mode was previously changed. Corresponding means successively initiating the switching at a bank outside of this, from the first one switched Bank or group specified time span.

In a further embodiment, a corresponding Procedure with an internal combustion engine with only one controllable throttle applied, with a cylinder group homogeneous and the other is stratified. In In this case, the air charge is increased by the throttle, so that a larger proportion of the desired torque value homogeneous control of a cylinder group with stoichiometric or lean mixture composition, while a smaller portion of the desired torque through stratified charge operation the other cylinder group is made.

Claims (10)

1. Method for operating an internal combustion engine having direct petrol injection, which internal combustion engine has at least two cylinder banks or cylinder groups which are operated in at least two operating modes, in both of which modes the injection of fuel is performed, characterized in that the at least two cylinder banks or cylinder groups are each controlled as a function of a predefined setpoint torque value and a predefined operating mode, one cylinder bank or cylinder group being operated in a first operating mode (BAsoll1) and the second cylinder bank or cylinder group being operated in the second operating mode (BAsoll2) in at least one operating state of the internal combustion engine, a variable setpoint torque value (Misoll1, Misoll2) being predefined for each of the cylinder groups and the torque of the respective cylinder bank or cylinder group being adjusted as a function of the said variable setpoint torque value.
2. Method according to Claim 1, characterized in that the setpoint torques for the two cylinder banks or groups are identical.
3. Method according to one of the preceding claims, characterized in that an overall setpoint torque value (Misoll) is predefined which controls a cylinder group or cylinder bank with a first part (Misoll1) of this overall setpoint torque value and controls another cylinder bank or group with a second part (Misoll2) of the setpoint torque, the two parts of the setpoint torque producing the overall setpoint torque.
4. Method according to one of the preceding claims, characterized in that the at least one operating state is the operating state of increased performance requirements and/or the operating state during which a storage catalytic converter is discharged.
5. Method according to one of the preceding claims, characterized in that the operating modes of the individual cylinder banks or groups are switched over one after another.
6. Method according to one of the preceding claims, characterized in that a desired operating mode (BAsoll) is predefined as a function of the operating state, which desired operating state is then implemented by controlling the individual cylinder banks or groups if this implementation does not contradict other instructions.
7. Method according to one of the preceding claims, characterized in that an electrically actuable throttle valve is provided for each cylinder bank or cylinder group, and the operating modes are switched over by controlling the said throttle valve.
8. Method according to one of the preceding claims, characterized in that only one electrically controllable throttle valve is provided for all the cylinder banks or cylinder groups, the said throttle valve being controlled during operation by different operating modes in the manner of an increased air charge compared with throttled operation, with the result that it is possible to operate a part of the cylinders in the first operating mode and another part in the second, unthrottled operating mode.
9. Method according to one of the preceding claims, characterized in that the operating modes of the individual cylinder banks or groups are switched over simultaneously, at least in an operating state with high performance or torque requirements.
10. Apparatus for operating an internal combustion engine having direct petrol injection, which internal combustion engine has at least two cylinder banks or cylinder groups which are operated in at least two operating modes, having at least one controller which controls the cylinder groups or cylinder banks of the internal combustion engine as a function of predefined setpoint torque values and predefined operating modes, characterized in that the controller comprises means which control the first cylinder bank or cylinder group in a first operating mode (BAsoll1) and control the second cylinder bank or cylinder group in a second operating mode (BAsoll2) in at least one predefined operating state, fuel being injected in each operating mode, and a variable setpoint torque value (Misoll1, Misoll2) being predefined for each of the cylinder groups and the torque of the respective cylinder bank or cylinder group being adjusted as a function of the said variable setpoint torque value.

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