DE102006023893A1 - Method and control unit for controlling an internal combustion engine with a firing angle torque reserve - Google Patents

Abstract

A method for adjusting an actual torque of an internal combustion engine (10) to a variable setpoint (T_setpoint) by ignition angle interventions in an ignition path (52) and by filling interventions in a filling path (54) is presented. The method is characterized in that the adjustment of the torque is additionally carried out by taking place in a fuel path (56) lambda interventions. Furthermore, a control device (33) set up to carry out the method is presented.

Description

State of the art

The The invention relates to a method according to the preamble of the independent method claim and a control unit according to the generic term of the independent Apparatus claim.

Such a method and such a control device is in each case from DE 195 17 673 known. The torque provided by an internal combustion engine depends essentially on the filling of its combustion chambers with combustible fuel / air mixture and the ignition angle in the working cycle of the internal combustion engine. For a given charge, there is an optimal ignition angle zw_opt at which the torque resulting from the combustion is maximum. At the subject of DE 195 17 673 the internal combustion engine is operated at least at idle with a suboptimal ignition angle. As a result, the torque is smaller than the value occurring at the optimum ignition angle zw_opt. To compensate for the internal combustion engine is operated with an increased combustion chamber filling. Adjusting the ignition angle at the increased combustion chamber filling in the direction of the optimum ignition angle zw_opt, the torque of the engine is increased with constant filling. The range of possible increases with constant filling is also referred to as the ignition-angle torque reserve. An ignition angle adjustment can be made from one ignition to the next ignition. Thereby, the torque of the internal combustion engine from one ignition to the other ignition can be increased by the ignition angle of the suboptimal base ignition angle is adjusted to the optimum ignition angle ZW_opt. Considering as an example a four-cylinder four-stroke engine at an idling speed of 600 min ^-1, so elapses between two successive firings a period of 50 ms. This period is shortened with increasing speed and number of cylinders. By contrast, the combustion chamber fillings which are also relevant for the development of torque react much more slowly to setting interventions. Between such a control intervention, for example, with which a throttle opening angle is increased, and the occurrence of a resulting larger torque passes a period of time, which is typically of the order of several 100 ms.

It It is understood that the ignition angle torque reserve be big enough must compensate for rapid fluctuations of disturbances of idle speed to be able to. A typical value of firing torque reserve is about 10%. This means, that the torque of the internal combustion engine by adjusting on the optimal ignition angle increased by 10% can be. But this also means that the internal combustion engine at the base firing angle with a correspondingly reduced thermodynamic efficiency and increased accordingly Idle fuel consumption is operated.

Disclosure of the invention

The Invention differs from this prior art the characterizing features of the independent claims.

Advantages of the invention

With the use of Lambda interventions occurring in a fuel path for the Setting the torque is provided an additional control action, the crankshaft angle synchronous and thus similar fast acts as the Ignition angle. The Air ratio lambda is known to be a quotient of an actual Combustion of a given mass of fuel available air mass in the counter and one for a stoichiometric Combustion of this fuel mass required air mass in the denominator. While Internal combustion engines for operated a consumption-optimal operation with lambda values greater than 1 be, takes place for optimized pollutant conversion in a three-way catalyst Operating at lambda = 1, and optimized for maximum performance Operation of the internal combustion engine takes place at lambda values, which is something less than 1, for example at lambda = 0.9. Idle and In idle part load range modern combustion engines with lambda <1 or lambda = 1 operated. That means that naturally a certain lambda torque reserve is available by adjusting of the lambda value can be retrieved to lambda = 0.9. For an estimate of the effect such enrichment one can assume that an enrichment by 10%, so an enrichment of, for example lambda = 1 to lambda = 0.9, generates about 3% to 5% more torque. In contrast to Ignition angle torque reserve is this lambda torque reserve not with a fuel penalty, so not associated with a fuel consumption. Because the lambda intervention is similarly fast takes place like the ignition angle intervention, allows the extra Using a lambda engagement to set a torque a reduction of the ignition angle torque reserve and thus a reduction in fuel consumption.

Further Advantages will be apparent from the description and the attached figures.

It is understood that the features mentioned above and those yet to be explained not only in the combination given, but also in other combinations or alone, without departing from the scope of the present invention.

Brief description of the drawings

embodiments The invention are illustrated in the drawings and in the following description explained. In each case, in schematic form:

1 an internal combustion engine with actuators, sensors and a control device, which is set up to control the sequence of embodiments of inventive method;

2 a system structure of the controller from the 1 ;

3 time profiles of a setpoint torque and manipulated variables in one embodiment of a method according to the invention; and

4 a flowchart as an embodiment of a method according to the invention.

Embodiments of the invention

1 shows an internal combustion engine 10 with at least one combustion chamber 12 that of a piston 14 is sealed movable. The combustion chamber 12 is via an intake system 16 filled with air or a mixture of fuel and air. Fillings of the combustion chamber 12 be through a spark plug 18 ignited. Exhaust gases of burned combustion chamber fillings are via an exhaust system 20 dissipated. The periodic change of the combustion chamber fillings is via at least one inlet valve 22 and an exhaust valve 24 controlled in the representation of the 1 through assigned camshafts 26 and 28 synchronous to a movement of the piston 14 be operated. The mass of the in the combustion chamber 12 flowing air is determined by the opening angle of a throttle valve 30 certainly. An air mass meter 32 serves to capture the in the internal combustion engine 10 flowing air mass.

To generate a combustible fuel / air mixture, the incoming air is fuel via an injector 34 or 36 added. The injector 34 is in the intake system 16 arranged and dosed the fuel in one embodiment in front of a valve disk of the intake valve 22 , This type of fuel metering is also referred to as intake manifold injection. Alternatively to the intake manifold injection with such an injector 34 can also be an injector 36 be provided, the fuel directly into the at least one combustion chamber 12 metered, which is also referred to as direct injection. In both alternatives, the injector 34 or the injector 36 from a controller 33 activated with injection pulse widths ti. Every injector 34 or 36 is connected to a fuel pressure accumulator, not shown, and opens during an injection pulse width ti a flow cross-section, is dosed via the fuel when applying the injection pulse width ti.

The position of the throttle 30 is from the controller 33 by controlling a Drosseiklappenstellers 38 set with a control signal S_DK. Furthermore, the control unit triggers 33 Burns out by removing the spark plug 18 with an ignition signal zw controls. The mass of the in the combustion chamber 12 fuel / air mixture included in combustion, its composition of fuel and air, and the timing or firing angle, which significantly affect the piston 14 transmitted energy and thus the internal torque of the internal combustion engine 10 , The ignition angle zw, the injection pulse widths ti and the control signals S_DK therefore provide essential control variables for setting a required torque of the internal combustion engine 10 represents.

The control unit processes these and other control variables to form these 33 Signals mL over in the internal combustion engine 10 flowing air mass, a signal FW, which characterizes a torque demand of a driver, a signal KWW, the angular position of a crankshaft and thus of the piston 14 of the internal combustion engine 10 represents a signal NWW, which is an angular position of one of the camshafts 26 or 28 represents and a lambda signal, which is a measure of the fuel / air mixture composition of the combustion chambers 12 burned fuel / air mixture is. The signal mL is from the air mass meter 32 provided. A driver's desire 40 detects the position of an accelerator pedal 42 and thus provides the driver request signal FW. A crankshaft angle sensor 44 feels marks 46 a donor wheel rotatably connected to the crankshaft 48 and delivers the signal KWW. The signal NWW is from a camshaft angle sensor 50 provided. An exhaust gas sensor 52 in the exhaust system 20 of the internal combustion engine 10 provides a measure of the air ratio lambda.

The control unit 33 of the internal combustion engine 10 is set up, in particular programmed, an actual torque of the internal combustion engine 10 through in a ignition path 52 taking place Zündwinkeleingriffe, so interventions on the firing angle zw, and through in a filling path 54 performing filling interventions, such as interventions on the opening angle of the throttle valve 30 to set to a variable setpoint T_soll. It operates the controller 33 the internal combustion engine 10 in an embodiment with increased combustion chamber fillings and sub-optimal ignition angles zw, that is to say with an ignition-angle torque reserve which is a riser Torque from one ignition to the next ignition allowed. The control unit 33 is also adapted to the actual torque of the internal combustion engine 10 additionally through in a fuel path 56 to discontinue lambda interventions. The lambda intervention preferably takes place via an enrichment, that is to say via an enlargement of an injection pulse width ti, wherein the increase in the torque requirement of the internal combustion engine 10 measured.

The 2 shows a system structure of the controller 33 from the 1 , The control unit 33 can be functionally in a first block 58 and more blocks 60 . 62 . 64 subdivide. The block 58 serves the processing and processing of the supplied input signals. In the presentation of the 2 these are the ones associated with the 1 explained signals KWW, NWW, FW, mL and lambda.

In a preferred embodiment takes place in the block 58 the formation of a target torque T_soll and the distribution of the target torque T_soll on the ignition path 52 , the filling path 54 and the fuel path 56 , Under stationary conditions, that is to say with a constant torque requirement, the following division results, for example: For realizing a torque of x Nm, the filling path is established 54 a magnifying engagement of, for example, a maximum of 1.08 · x Nm is required, from the fuel path 56 a neutral engagement 1 · x Nm and from the ignition path 52 a reduction intervention 1: 1.08 · x Nm required.

These claims are made about the blocks 60 . 62 and 64 in corresponding manipulated variables S_DK in the air path 54 , ti in the fuel path 56 and zw in the ignition path 52 converted. About the filling path 54 So is a filling of the combustion chamber 12 which would deliver 8% more torque at the optimum firing angle than required for steady state operation. At the same time a sub-optimal ignition angle zw is set via the ignition path. Compared to the torque at an optimal firing angle, at the suboptimal firing angle, only 1: 1.08 times the optimum torque is generated. In the interaction of the air path 54 and the ignition path 52 This results in the 1.08: 1.08 times the desired torque with a firing torque reserve of 8%.

In the event of a changing torque request, a changed distribution of the torque requests to the blocks takes place 60 . 62 . 64 or to the filling path 54 , the fuel path 56 and the ignition path 52 , The changing torque request is divided into fast and slow shares. The slowly changing parts are over the filling path 54 are set and the rapidly varying proportions are via the crankshaft angle synchronous paths 52 and 56 set. An example of a slowly varying portion is represented by the integral portion of an idle speed control, while proportional and / or derivative portions of such idle speed control are examples of rapidly varying proportions.

The 3 shows curves of a variable setpoint torque T_soll and manipulated variables in one embodiment of a method according to the invention over time t. It shows the 3a the course of a target torque T_soll, which jumps at a time t1 from a first setpoint T_soll1 to a second, higher setpoint T_soll2. Such a jump in the torque request results, for example, in an idle speed control when an additional load occurs, which is to be provided by the engine. A typical example is the connection of an air conditioning compressor. In the case of 3a exceeds the difference dT_soll from the new setpoint T_soll2 and the old setpoint T_soll1 a threshold S.

The block 58 out 2 , in which the idle speed control is integrated, then distributes the increased torque request with time gradients on the ignition path 52 , the fuel path 56 and the air path 54 as it is qualitatively in the 3b - d is shown.

In this case, a P component of the idle speed control on the two crankshaft angle synchronous paths 52 and 56 distributed. The manipulated variable change takes place in the ignition path 52 a little faster, in the presentation of the 3 at time t1, as the manipulated variable change in the fuel path 56 at time t2, because the mixture formation by an injection pulse width ti necessarily always has to be done some crank angle degrees before ignition. However, it is essential that a certain proportion dT (lambda) in the fuel path 56 can be provided. This allows the share dT (zw) of the over the ignition path 52 To be set torque change lower than this without an intervention in the fuel path 56 the case would be.

The preceding comparison of the required setpoint change dT_soll with the threshold value S ensures that the lambda interventions in the fuel path 56 only take place if the magnifications of the setpoint dT_soll are greater than the available torque reserve. In that first the torque reserve of the ignition path 52 is used and interferes with the fuel path 56 only if dT_soll> S_act, small torque changes dT_soll are compensated by the firing torque reserve, which has a positive effect on the force material consumption. The intervention in the ignition path 52 improves the efficiency. The intrinsic efficiency degrading enrichment in the fuel path 56 is limited to the necessary cases where the required change dT_soll of the torque setpoint T_soll exceeds the threshold value S.

3d shows the time course of the procedure on the filling path 54 , In the illustrated embodiment takes over the filling path 54 the integral part of an idle speed control. About the filling path 54 , via which the base torque T_basis is provided, there is therefore successively an increase in the torque of the internal combustion engine 10 from the time t1 until the time t3, the new required target torque T_soll2 is reached. Parallel to the increase of the base torque T_basis, that over the filling path 54 between times t1 and t3, the paths in the crankshaft angle synchronous paths may be adjusted 52 and 56 set torque components dT (zw) and dt (lambda) are reduced. 3 discloses thus in particular a method which reacts to increases of the setpoint t_setpoint with a comparatively rapid reduction of the torque reserve due to the sudden increase of dT (zw) and with a comparatively slow change of the filling, or of the base torque T_basis, wherein the torque reserve with increasing effect of Change of filling is increased again. At time t3, the intervention is dT (zw) in the ignition angle path 52 again dropped to its neutral value, so that the full torque reserve is available again.

The height of the threshold value S in this embodiment corresponds to the maximum value of dT (zw). This division ensures that the torque reserve after a certain settling time of the filling path 54 is again available for new setpoint changes.

In a preferred embodiment, the method is used when the internal combustion engine 10 is operated at idle and / or in an idle speed and / or target torque range with the torque reserve. As a result, the fuel disadvantage of the torque reserve is limited to these areas.

In a preferred embodiment, the factor 1.08 mentioned for this embodiment represents an upper limit for the ignition-angle torque reserve. To the fuel disadvantage of the intervention in the fuel path 56 to minimize, the maximum engagement is limited so that resulting lambda values are definitely greater than lambda = 0.9. This also limits the occurrence of hydrocarbon emissions. In conjunction with the gradual taking over of the torque engagement through the filling path, or through the filling path 54 If the base torque T_basis is set, the time period during which enrichment which is disadvantageous for consumption and emissions per se is also limited.

4 shows an embodiment of a method according to the invention in conjunction with an idle speed control LLR, the in step 68 is started. In step 70 the formation of a control deviation dn takes place as the difference of a speed setpoint n_setpoint and an actual speed value n_actual. The actual speed value n_act may be, for example, as a time derivative of the crankshaft angle signal KWW of the crankshaft angle sensor 44 from the 1 be formed. To reduce a positive dn, this must be done by the internal combustion engine 10 generated inner moment to be increased. This is done in step 72 the formation of a change dT_soll as a function f (dn, ...). The comma and the points in the argument of t indicate that t may depend on further operating parameters. In step 74 will that be in the step 72 formed dT_soll compared with the threshold value S. As long as the threshold S is not exceeded, the torque request in step 76 by intervening on the fast, crankshaft angle synchronous ignition path 52 and the slow filling path 54 Fulfills. This sees step 76 the formation of an ignition angle zw as function f1 (dT) and the formation of a throttle position signal S_DK as function f2 (dT). If the threshold S in step 74 on the other hand, the program branches into the step 78 in which, in addition to the formation of ZW and S_DK, the formation of an intervention in the fuel path 56 takes place, in which the injection pulse width ti is formed as a function f3 (dT). S_DK and zw can step in 78 with the same dependencies f2 (dT) and f1 (dT) as in the step 76 be formed.

So far As previously described, the lambda interventions are in addition to Ignition interventions at an internal combustion engine used in certain operating points with a Zündwinkeldrehmomentreserve is working. An example of such an operating point is the work area an active idling control.

In one embodiment, the adjustment of the torque through in the fuel path ( 56 ) take place in the ignition path taking place ignition angle wholly or partially. In other words, the additional possibility of increasing the torque via a lambda intervention is used to set the operating point of the internal combustion engine so that the ignition-field torque reserve is as low as possible. In further embodiments dT (zw) can be used in one, several or all operating points of the Ver be equal to zero, so that the internal combustion engine operates at such an operating point with a crankshaft angle synchronous torque adjustment and a complementary intervention on the air path or filling path.

A further embodiment provides that torque-reducing interventions are initially made in the fuel path and that a deterioration of a Zündwinkelwirkungsgrades by one in the ignition path ( 52 ) takes place ignition engagement only if a setting range of the lambda engagement is not sufficient to achieve a desired reduction in torque. In the fuel path, the reduction in the torque can be achieved by increasing the lambda value, that is to say by emaciating the fuel / air mixture.

Claims (13)

Method for setting an actual torque of an internal combustion engine ( 10 ) to a variable setpoint (T_setpoint) in a firing path ( 52 ) Zündwinkeleingriffe and by in a filling path ( 54 ) filling operations, characterized in that the adjustment of the torque additionally by in a fuel path ( 56 ) takes place lambda interventions. Method according to claim 1, characterized in that the adjustment of the torque through in the fuel path ( 56 ) Lambda interventions which takes place in the ignition path Zündwinkeleingriffe completely or partially replaced. A method according to claim 1 or 2, characterized in that torque-reducing interventions are initially made in the fuel path and that a deterioration of a Zündwinkelwirkungsgrades by one in the ignition path ( 52 ) takes place ignition engagement only if a setting range of the lambda engagement is not sufficient to achieve a desired reduction in torque. Method according to one of the preceding claims, characterized in that the internal combustion engine ( 10 ) is operated with a firing torque reserve, which allows an increase of the torque from one ignition to the next ignition. Method according to one of the preceding claims, characterized characterized in that on enlargements of the setpoint (T_set) with a comparatively fast reduction the torque reserve and with a comparatively slow change the filling is reacted, the torque reserve with increasing effect the change the filling is enlarged again. Method according to claim 5, characterized in that that enlargements of the setpoint with that for disposal standing torque reserve are compared and that the lambda interventions only occur when the magnifications of the setpoint are greater than the available standing torque reserve is. Method according to one of the preceding claims, characterized in that the internal combustion engine ( 10 ) is operated at idle and / or in an idle speed and / or target torque range with the torque reserve. Method according to Claim 7, characterized in that the internal combustion engine ( 10 ) is operated at a control of its idle speed with the torque reserve. Method according to claim 8, characterized in that that proportional and / or differential components of the scheme of Idle speed due to ignition interventions and / or lambda interventions are realized and that an integral part the regulation of the idle speed realized by Füllingseingriffe becomes. Method according to one of the preceding claims, characterized characterized in that a maximum value of the torque reserve is smaller is equal to or equal to 0.08 times a torque value that is for a given filling and in terms of torque development, optimum values for lambda and the ignition angle results. Method according to one of the preceding claims, characterized in that the lambda interventions in the fuel path ( 56 ) are limited so that resulting lambda values are greater than 0.9. Control unit ( 33 ) of an internal combustion engine ( 10 ), which is adapted to an actual torque of the internal combustion engine ( 10 ) by in an ignition path ( 52 ) Zündwinkeleingriffe and by in a filling path ( 54 ) to set to a variable setpoint (T_setpoint), characterized in that the control unit ( 33 ) is adapted to the actual torque additionally by in a fuel path ( 56 ) Lambda operations take place. Control unit ( 33 ) according to claim 4, characterized in that it is adapted to control the sequence of a method according to one of claims 2 to 3.