EP1774158A1

EP1774158A1 - Device and method for control of an internal combustion engine

Info

Publication number: EP1774158A1
Application number: EP05769811A
Authority: EP
Inventors: Jochen Laubender
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-07-30
Filing date: 2005-07-25
Publication date: 2007-04-18
Also published as: JP2008508461A; US20070039582A1; WO2006013167A1; DE102004037131A1

Abstract

The invention relates to a method and a device (1) for control of an internal combustion engine (500), whereby a determination means (410) recognises a possible self-ignition operating condition before a start of the internal combustion engine depending on operating parameters and determines suitable operating parameters to prevent said possible self-ignition operating state.

Description

Device and method for controlling an internal combustion engine

The invention relates to a device for controlling an internal combustion engine according to the preamble of the first independent main claim. Furthermore, the invention relates to a method according to the species of the second independent main claim.

State of the art

In order to reduce the consumption and emissions of motor vehicles, so-called start-stop methods are increasingly being used. In the current start-stop method, the engine is started by means of an electric machine, such. B. one

Belt or crankshaft starter generator or even a conventional starter. Typically, the start takes place by a torque of the internal combustion engine being generated when the internal combustion engine is accelerated by injecting fuel and subsequently igniting, the starter being disengaged again when the engine rpm is sufficient.

A starting device is known from EP 1 036 928 A2, in which at least one cylinder in compression is identified when the internal combustion engine is switched off, and in the presence of a start request, fuel is injected into this cylinder.

However, the problem with the starting device described in EP 1 036 928 A2 is the injection of fuel into a compression phase at high engine temperatures. When the engine is started from "deep" piston positions close to BDC (bottom dead center), the trapped mixture reaches temperatures above 400 ^° C in the compression phase, which can partially trigger auto-ignition reactions

Part acoustically perceptible as knocking combustion and must, for reasons of construction Partial protection can be avoided. Since this problem of auto-ignition can occur particularly frequently in a start-up of an internal combustion engine during start-stop operation of a vehicle and also in very short time intervals one after the other, it must be guaranteed in this operating mode that self-ignition is reliably prevented ,

Self-ignition is a function of various engine parameters (engine temperature, charge, general engine metric data, such as compression ratio), mixture composition (lambda, fuel grade, etc.) and injection timing. Depending on the prevailing conditions in the cylinder, it usually occurs close to the TDC position (= moment of the highest compression temperature) and thus limits important engine functions programmed in the control device, such as, for example, Functions which are intended to control the efficiency of the engine torque output by means of an adjustment of the ignition angle greatly or make their execution impossible. As a result, the engine, depending on the current torque request, u.a. not optimally operated, which has a negative effect not only on the running culture of the engine, but also on the consumption and sometimes also on the resulting emissions. Advantages of the invention

The device according to the invention with the features of the independent claim has the advantage that a calculation means before a start of Brennkraft¬ machine detects a possible autoignition operating state as a function of Be¬ operating parameters and determines suitable control variables to prevent this possible Selbstentzündungs- operating state.

The corresponding method according to the invention with the features of the associated independent claim has the advantage that a possible self-ignition operating state is detected before starting the internal combustion engine as a function of operating parameters, and suitable control variables for preventing this possible auto-ignition operating state be determined.

As a result of the procedure according to the invention, it is advantageously possible to ensure, even before a start of the internal combustion engine, that is before the crankshaft is set in motion, that operating parameters indicative of a possible spontaneous ignition of the fuel during the start, suitable control variables are determined based on which components of the internal combustion engine, in particular a starter or an injection device, are controlled during the start such that a self-ignition of the fuel or a Selbstentzündungs- operating state is prevented.

Advantageous further developments and improvements of the method specified in the independent claim are possible due to the measures listed in the subclaims.

It is particularly advantageous if, depending on the control variables, at least one starter and / or an injection device is influenced. This allows a starter to be operated in such a way that, for example, the adjusting piston movement is such that auto-ignition of the fuel is avoided. If, in addition, the injection is also acted upon, then both can be matched to one another in an advantageous manner.

Furthermore, it is advantageous if at least the position of a cylinder which initially goes into compression or into a suction cycle when starting and / or a variable which represents a combustion chamber temperature is taken into account as the operating parameter. If the position of a first compression-going cylinder is known, the control variables can be selected, determined or calculated in such a way that self-ignition is avoided. If, in addition, the combustion chamber temperature or, as the case may be, the engine or oil temperature is known, the control variables can be determined more precisely in order to avoid self-ignition.

A further advantageous embodiment provides that the injection is influenced such that in a direct-injection internal combustion engine, the fuel injection takes place only after the going into compression cylinder has passed through its top dead center. This procedure has the particular advantage that the fuel is injected only in the expansion phase and thus prevents spontaneous combustion of the fuel, since during the compression phase only fresh air and no fuel-air

Mixture is compressed.

According to a further advantageous embodiment, it is provided that the rotational speed of the starter is influenced such that the combustion chamber temperature remains below a critical temperature threshold. This has the advantage that, especially when the speed is reduced near top dead center, the temperature increase is more moderate - A -

and a critical temperature threshold at which the fuel can ignite itself is avoided.

A further advantageous modification provides that the rotational speed of the starter is influenced in such a way that the combustion chamber pressure remains below a critical pressure threshold.

This results in the advantage that, in particular with a reduction in the speed in the vicinity of top dead center, the pressure increase is more moderate and a critical pressure threshold at which the fuel can ignite itself is avoided.

Finally, a further embodiment provides that an injection quantity is increased in such a way that the combustion chamber temperature remains or falls below a critical temperature threshold. By an increased fuel supply, the air / fuel mixture is abge¬ cooled, so that advantageously an auto-ignition can be avoided.

drawings

Show it

FIG. 1 schematically shows a sequence of a start-stop operation; Figure 2 shows schematically the monitoring of the motor run-up; 3 shows schematically a control device according to the invention.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the drawings. All features described or illustrated alone or in any combination form the subject matter of the invention, regardless of their combination in the claims or their dependency and regardless of their formulation or representation in the description or in the drawings.

description

The invention is based on the consideration of recognizing already before a start of the internal combustion engine on the basis of operating parameters whether the danger of possible fuel self-ignition exists during the start and engine run-up. If a potential auto-ignition operating state is detected, this will be prevented Operating state suitable control variables for the start of the internal combustion engine determined or adjusted.

In particular, it is helpful in the case of direct-injection internal combustion engines to determine the piston position of the cylinder that is initially in compression and to determine the piston position of the cylinder that first goes into the suction phase in internal combustion engines with intake manifold injection.

For example, an absolute angle sensor can be used to identify the starting cylinder, which is mounted on the camshaft and / or crankshaft and the instantaneous

Indicates the angular position of the crankshafts. The absolute angle sensor also makes it possible to synchronize the control unit more quickly with the internal combustion engine than is possible with the conventional synchronization methods via reference marks on the crankshaft sensor wheel and / or a phaser wheel on the camshaft.

The exemplary embodiment of a start-stop operation shown schematically in FIG. 1 shows, by way of example, a possible field of application or technical environment of the invention.

The exemplary start-stop operation is as follows: In step 10, the controller is in a pre-start phase. In the start-stop mode, the ignition remains

(KLl 5) either turned on or is briefly energized at defined intervals, so that the control unit is applied regularly to the supply voltage. As a result, the otherwise necessary resynchronization of the control unit with the motor during startup becomes unnecessary, and the various operating parameters of relevant motor functions are regularly updated. Alternatively, this task can also be taken over only by a special partial function in the control unit during the stop phase, so that the entire control unit does not always have to be activated.

In step 20, relevant operating parameters are then detected. The following operating parameters are, for example, possible as input variables: starting cylinder, piston position, engine, engine oil, cooling water, intake air, ambient air, catalyst and fuel temperature, fuel rail, ambient air pressure, fuel quality, battery voltage, valve timing, -hub, compression ratio, gear, clutch, position throttle, accelerator pedal, brake pedal position, time and others. Based on the acquired or determined operating parameters, a start strategy is determined based on the control variables for a motor run-up. A starting strategy may, for example, take into account a cold repeat or hot start or a start-stop operation or be designed to realize a fast engine run-up or further strategies for achieving an optimal engine run-up. According to the invention, it is provided, for example, in this step 20 or also in the subsequent steps, to check on the basis of the determined operating parameters whether a self-ignition operating state may possibly occur at the start or when starting the engine. If such an operating state is forecasted, it is provided that the starting strategy and the control variables are coordinated in such a way that a self-igniting

Operating state is prevented.

In step 30 it is checked whether the start strategy can be performed. If conditions for the start strategy are unfavorable or not fulfilled, branching is made to step 100, in which a decision is made as to whether a cylinder succeeding in the firing sequence is selected - step 100 - or whether an alternative start procedure is initiated - step 120.

If suitable conditions for carrying out the starting strategy are present, relevant control variables are read out in step 40.

Relevant control variables are, for example: injection time, angle, quantity; Ignition time, angle; to be delivered engine torque; Time or angle duration of the control of the starter; Valve timing, stroke; Compression ratio; Throttle valve position, exhaust gas recirculation valve and others.

In step 50, the control variables are output to the respective components, for example an injection device and / or a starter, and in step 60 the starting of the internal combustion engine then takes place.

In the following step 70, it is preferably checked after a first power stroke whether the control variables have led to an engine run-up given in accordance with the starting strategy while avoiding the predicted auto-ignition. In the event of deviations from the setpoint engine run-up, the control variables are adapted in step 200 so that the desired engine run-up is achieved. In step 50, the new control variables are then also provided under the condition of a reliable prevention of auto-ignition effects. spent on the components. Step 60 is skipped in this cycle and checked again in step 70 whether the engine run-up follows in accordance with the starting strategy. In the case of deviations, the control values may be adjusted again via step 200.

As a fallback level in the event that the start was unsuccessful, in the examination in step 70 a branch is made to step 120, in which an alternative start procedure is then initiated.

Upon a successful start, step 80 follows, in which the engine enters the engine

Normal operation is brought.

If there is a stop request, the shutdown of the internal combustion engine is regulated or unregulated, depending on the parking concept. With a branching into the step 90, an uncontrolled engine shutdown is initiated, in which the crankshaft runs out freely without influencing. If a regulated engine shutdown is provided, the step 190 follows. A regulated engine shutdown lifts off to put an internal combustion engine and in particular the crankshaft in a defined state, so that in a subsequent start an optimal piston position with regard to avoid auto-ignition, shortened start time, optimal engine run-up, lower on-board network load, better mixture preparation is achieved.

After the engine shutdown in step 90 or 190, reference is made to the pre-start step 10, with which a new operating cycle can begin. If no conditions for carrying out the starting strategy are provided in step 30, the method branches to step 100 as described. Preferably, an attempt is made to find a cylinder for which the conditions are fulfilled, that is, for example, the cylinder has a suitable piston position. Thus, step 100 initially branches to step 110. Here, a cylinder following in the ignition sequence is selected and branched into step 20, so that the routine can run again. If no suitable condition is registered again in step 30, the loop is typically repeated in step 100 until all cylinders have been interrogated. If there is still no suitable condition, step 100 branches to step 120 and initiates an alternative startup procedure. In step 120, the present start strategy is initially aborted. A possible starting alternative is to have control variables for a non-optimized engine start-up, which, however, also preferably also reliably avoids autoignition, should be kept ready. By way of example, these control variables may be selected such that standard values are used for the injection and the ignition, whereas the starter may be controlled with control variables for a preferred starting strategy, for example a start-stop operation. As a further alternative, it may also be provided to initiate a "classic" normal start in which the starter is operated in a conventional manner.

In the following step 130, the control variables are output to the components, after which the start takes place in step 140, wherein it is then checked in step 70 whether the start was successful.

In the event that the engine does not start, the process branches back from step 70 to step 120 and a retry attempt is made. After repeated

Start failure may also be provided to initiate appropriate error responses.

FIG. 2 shows in detail the steps after starting the internal combustion engine in step 70. As already described in FIG. 1, in step 40 control values are read out according to the starting strategy and output to components 300 of the internal combustion engine in step 50, wherein then in step 60 (not shown in Figure 2) a start. After the start of the start, operating parameters are read in, for example, continuously or at specific time intervals, essentially independently of the remaining steps in a step 220, so that, if necessary, a time profile of relevant operating parameters can be determined.

After the start of the startup, it is checked in step 70 on the basis of the operating parameters determined in step 220, whether an engine start-up is present while avoiding spontaneous ignition according to the predetermined starting strategy. If the determined operating parameters deviate from the operating parameters expected according to the start strategy, in step 200 the

Control values adjusted so that the desired engine run-up is achieved. The new control values are output to the components 300 in step 50 and the success is checked in step 70 and, in the case of renewed deviations, branched back into step 200. In FIG. 3, a device 1 according to the invention for controlling an internal combustion engine 500 is shown with a dashed border. The device 1, preferably a control device, comprises a calculation means 410, a detection means 420, a control means 430 and a storage means 440.

The detection means 420, preferably a receiver, analog-to-digital converter or the like, detects operating parameters of the internal combustion engine and forwards corresponding signals to the calculation means 410 and the control means 430 on. The calculation means 410, preferably a microprocessor or in general a computing unit, calculates or determines, on the basis of the acquired operating parameters, one for a start of the

Internal combustion engine suitable start strategy and sets control variables so that the Mo¬ tor run-up according to the desired start strategy with safe avoidance of Selbst¬ inflammation effects. The control variables and possibly the start strategy are passed on to the control means 430. The control means 430 may, for example, be constructed as a separate unit or else be part of the functionality of the calculation means. About the control means 430 and possibly other functional modules components of the internal combustion engine are controlled with the specified control variables. The control means 430 monitors on the basis of detected operating parameters whether the engine run-up at the start corresponds to the predetermined start strategy. If the engine run-up or certain operating parameters deviates from the parameters expected for the start strategy, the control means 430 adjusts the control variables accordingly in order to achieve an optimum engine run-up in accordance with the desired start strategy. The adapted or adapted control variables are stored in a memory means 440, so that values which have already been adapted are available for a renewed start with a corresponding start strategy.

To output the control variables in accordance with the start strategy, the control variables can be stored, for example, in maps, lines, special value tables, storage units of a neural network or other storage units and can also be learned adaptively, so that a start that is optimized in terms of time, consumption and emissions is always achieved becomes.

Depending on the operating parameters, in each case the optimal starting strategy and corresponding control variables are determined and determined in order to achieve optimum starting conditions for the internal combustion engine. If, despite the preselected control variables, non-optimal operating states still occur, for example fuel self-ignitions, the control variables are selected for the next start such that a renewed occurrence of these

Effects is prevented. However, it must then be ensured that the new election of However, a 100% Startzuver¬ permeability is achieved, if necessary, the pilot control values are also adjusted.

Alternatively, you can also switch to operation with a classic starter start (= longer spin of the starter). The same applies after a start abort or an unsuccessful attempt to start during a start-stop operation.

If, in general, the conditions for a successful "starter-assisted direct start", for example, after the ambient conditions in the engine have not been completely fulfilled before the start for the respective starting cylinder, for example in the event that the piston position of the starting cylinder is not optimal, then starter rotation can also be used , which leads in the firing sequence subsequent cylinder from the intake into the compression stroke and the start routine performed on this cylinder.

A device or control device according to the invention with motor control functions programmed therein makes it possible to output injection and ignition pulses separately from one another and at arbitrary times or crankshaft angles. It also makes it possible to control an electric machine, such as a starter or starter-generator, with time-variable or variable control over the cam or crankshaft angle. Likewise, in systems with variable compression or valve control, it is possible to vary the compression ratio or the phase and stroke position of the intake and exhaust valves during the starting process.

In systems with variable valve timing, moreover, by adjusting the valve timing for intake and exhaust camshafts, either the degree of filling in the

Compression phase and the output engine torque can be controlled. In the compression phase, e.g. by a later or earlier closure of the inlet valve, the degree of filling in the compression cylinder can be changed depending on the ambient conditions in the engine.

For example, a possible start strategy can provide a special control algorithm and thus predict or simulate the temperature profile during the compression phase on the basis of the compression ratio, the air mass included in the cylinder and the starter speed. Thereafter, the output variables of the control algorithm or the control values can be set in such a way that a critical temperature for auto-ignition is not exceeded. In systems with variable compression, the compression ratio can additionally be varied during the compression and combustion process so as to control the compression temperature and the compression pressure. Detects, for example, based on a temperature or combustion chamber pressure sensor, that the compression temperature or the

Compression pressure is too high, the compression of the engine is reduced (= expansion of the cylinder to larger displacement). Conversely, if the compression temperature or the compression pressure is too low for optimum mixture preparation, the compression ratio of the engine is increased.

In the procedure according to the invention, the problem of auto-ignition at high engine temperatures is prevented by targeted coordination of compression, injection and ignition.

The upstream activation of a starter as a start-supporting measure takes place in such a way that a possible spontaneous combustion is reliably prevented in the compression phase. This may mean, on the one hand, that the starter is power controlled in such a way that it starts in the compression phase, depending on the piston position, so that a certain rise in temperature or pressure in the combustion chamber is achieved during compression.

On the other hand, however, the triggering of the starter can also take place in such a way that an optimum in the mixture preparation time for the subsequent combustion is created during the compression phase on the basis of the starter speed. Should be meant that e.g. depending on fuel quality, engine, cooling water, oil temperature; Ver¬ seal the engine, etc., the starter speed and the resulting Kolbenge¬ speed, is controlled so that in the compression phase in the cylinder as homogeneous as possible fuel-air mixture is formed, which is then ignited.

By specifically monitoring the combustion chamber temperature by means of, for example, a temperature sensor or also a pressure curve of a combustion chamber pressure sensor, the compression temperature can be kept below the critical temperature for spontaneous combustion by specifically delivering heat to the cylinder wall. In addition, depending on the starting position, the starter is controlled either by angle or time based only as long as it is necessary to ensure the predefined speed when sweeping over the TDC. This means that the starter is actively discarded as early as possible in order to avoid unnecessary on-board network loads and / or start-up noise.

As a starting cylinder for the first combustion, the cylinder is also used in Kompressions¬ clock, which is identified before the start, for example by means of an absolute angle sensor on the crankshaft.

As described, it is also provided, not primarily before or during the compression phase in the compression cylinder, but only after sweeping the upper dead center, ie when the piston is already in the expansion phase of the working stroke, fuel into the cylinder inject and then ignite the air-fuel mixture.

The primary injection after TDC has several advantages: On the one hand, the problem of self-ignition is prevented by the fact that no premixed air-fuel mixture, but only fresh air is compressed. Thus, there is no ignitable mixture in the cylinder during the compression phase, which can ignite spontaneously due to the high compression temperatures. Unintentionally knocking burns, which can damage the engine, are thus effectively suppressed. On the other hand, the choice of ignition timing is not limited by the avoidance of autoignition, so that the combustion moment produced, and thus directly the ab¬ given engine torque, can be controlled by varying the injection and ignition timing and the amount of fuel so that the engine run-up defined speed curve follows and so eg Engine vibrations that may occur due to the first burns (= full load burns) and occur e.g. disturbing to the vehicle interior (= loss of comfort), minimized or prevented, or even an overshoot in the speed over the

Target idle speed, as currently occurs mostly during the startup process, can be reduced, so that the engine reaches its desired operating state faster. A quick achievement of the desired operating state of the engine is es¬ sentiell in start-stop operation for a quick start after a traffic light stop, for example. In addition, a reduced overshoot in speed also affects the starting noise of the engine out. A "whine" of the engine by an excessive speed at startup is thus effectively suppressed.

The sequence of injection and ignition can take place both time-based and angle-based. In addition, this starting method can also be applied to the second and further combustion processes following in the firing sequence in order to reliably avoid auto-ignition effects there as well.

That is, the start routine as shown in Figs. 1 and 2, respectively, controls. Based on the speed, or speed gradient curve of the previous combustion je¬ Weils the parameters (injection timing, quantity, ignition) for the subsequent combustion to safely avoid auto-ignition effects or to achieve a time, consumption and emission-optimized start.

Alternatively, the injection and ignition pulses may vary depending on the above

Input variables or operating parameters, however, also before or during the compression phase, i. even before reaching top dead center. However, it must be ensured on the basis of the input variables (for example engine, cooling water, oil, intake air temperature, etc.) that possible auto-ignition effects can be reliably ruled out.

This can, as described above, e.g. can be achieved by selective control of the starter, for example by monitoring the compression temperature and keeps ge by targeted wall heat losses to the cylinder wall below a critical temperature threshold for auto-ignition.

A further alternative, as described, is an increased injection quantity (enrichment) for the first burns, since in this way the air enclosed in the cylinders is cooled off more strongly (higher enthalpy of vaporization), thus bringing the temperature in the combustion chamber below the autoignition temperature can be.

In addition, the invention is also suitable for a start-stop system in vehicles with intake manifold injection (SRE). In this case, the injection pulses must take place for the individual cylinders during the intake stroke when intake valves are open or upstream into the intake manifold when intake valves are still closed. Thus, even with these systems during hot startup, a possible autoignition can be reliably prevented. The starter drive is then only slightly longer than the maximum drive time of the starter of about half a crankshaft revolution (about 180 ⁰ KW) in BDE systems with injection into the compression stroke. The starter is controlled as described in the systems with direct injection to avoid auto-ignition effects.

The risk of auto-ignition at high engine temperatures is limited in SRE start-stop systems by e.g. to prevent an increased injection quantity (enrichment) during the intake stroke or shortly before opening the intake valves (EÖ). By an upstream

Injection into the intake manifold shortly before EÖ or during the intake stroke, the Ansaug¬ air, which during e. a stop phase in the start-stop operation by the abgegebe¬ ne engine heat and also excessively heated by strong sunlight, cooled due to the evaporation of the liquid fuel. Thus, the temperature of the fuel-air mixture is significantly lowered and can be kept in the subsequent Verdich¬ tion below the temperature threshold for auto-ignition. In start-stop operation, a deterioration in emissions due to an increased injection quantity would be rendered harmless by the already heated catalyst and would thus be unproblematic. However, it must be ensured that while e.g. a long stop phase, the temperature in the catalyst does not fall below the conversion temperature.

Claims

claims

1. A device (1) for controlling an internal combustion engine (500), characterized gekenn¬ characterized in that a calculation means (410) before starting the internal combustion engine detects a possible auto-ignition operating state as a function of Betriebsparame¬ ter and to prevent this possible Selbstentzündungs- operating state determined suitable control variables.

2. A method for controlling an internal combustion engine, characterized in that prior to a start of the internal combustion engine as a function of operating parameters, a possible autoignition operating state is detected, and to prevent this possible autoignition operating state suitable control variables ermit¬ be determined.

3. Device or method according to claim 1 or 2, characterized in that depending on the control variables, at least one starter and / or a Ein¬ injection device is influenced.

4. A device or method according to at least one of the preceding claims, characterized in that for the determination of the control variables as Betriebspara¬ meter at least the position of a first going into compression or in a suction cycle at start cylinder and a size that represents a combustion chamber temperature reprä¬ , be taken into account.

5. Apparatus and method according to claim 4, characterized in that an intake air temperature is taken into account for the determination of the control variables.

6. A device or method according to at least one of the preceding claims, characterized in that in a direct-injection internal combustion engine, the

Fuel injection is influenced such that the fuel injection occurs only after the compression cylinder has passed through its top dead center.

7. The device or method according to at least one of the preceding claims, characterized in that the rotational speed of the starter is influenced such that the combustion chamber temperature remains below a critical temperature threshold.

8. The device or method according to at least one of the preceding claims, that the rotational speed of the starter is influenced such that the combustion chamber pressure remains below a critical pressure threshold.

9. A device or method according to at least one of the preceding claims, characterized in that an injection quantity is increased such that the combustion chamber temperature remains below a critical temperature threshold or falls.