ITMI20071008A1 - PROCEDIMENT AND CONTROL UNIT FOR COMMANDING AN INTERNAL COMBUSTION ENGINE WITH AN IGNITION AND TORQUE RESERVE - Google Patents

Description

DESCRIPTION

State of the art

The invention relates to a method according to the introductory definition of the independent claim concerning the method and a control apparatus according to the introductory definition of the independent claim regarding the device.

Such a method and such a control apparatus are respectively known from DE 195 17 673. The torque supplied by an internal combustion engine substantially depends on the filling of its combustion chambers with a combustible fuel / air mixture and on the ignition angle. in the duty cycle of the internal combustion engine. For a given filling there is an optimum ignition angle zw_opt, with which the torque resulting from combustion is maximum. In the basis of the subject matter of document DE 195 17 673 the internal combustion engine is operated, at least when idling, with a suboptimal ignition angle. Consequently, the torque is smaller than the value obtained with the optimum ignition angle zw_opt. To compensate, the internal combustion engine is operated with a greater filling of the combustion chamber. If, when the filling of the combustion chamber is greater, the ignition angle is shifted in the direction of the optimum ignition angle zw__opt, if the filling remains the same the torque of the internal combustion engine increases. The band width of possible increments with filling that remains the same is also called the ignition angle and torque reserve. An adjustment of the ignition angle can take place from one ignition to the next ignition. As a result, the torque of the internal combustion engine can also be increased between firings by shifting the firing angle from the basic, suboptimal firing angle to the optimal zw_opt firing angle. For example, if we consider a four-stroke and four-cylinder engine with an idle speed of 600 min <'1>, a time interval of 50 ms passes between two successive ignitions.

This time interval is further shorter as the speed and number of cylinders increase. The filling of the combustion chamber, which is equally important for the delivery of torque, on the other hand, reacts substantially more slowly to adjustment interventions. Between such an adjustment intervention, with which for example the opening angle of the throttle valve is increased, and the occurrence of a larger resulting torque, there passes a time interval which typically has an order of magnitude of several hundreds of ms. .

The reserve of ignition angle and torque must obviously be large enough to be able to compensate for rapid fluctuations of disturbance variables in the idling speed. A typical value of the ignition angle and torque reserve is around 10%. This means that the torque of the internal combustion engine can be increased by 10% by adjusting to the optimum ignition angle. However, this also means that the internal combustion engine is operated at a correspondingly lower thermodynamic efficiency and at a correspondingly higher minimum fuel consumption in the case of the basic firing angle.

Disclosure of the Invention

The invention differs from this state of the art for the characteristics which characterize the independent claims.

Advantages of the invention

By exploiting intervals on the lambda, taking place in a section of the fuel, an additional regulation intervention is made available for torque regulation, which acts in synchrony with the crank angle and therefore with a speed similar to that of the intervention on the angle. ignition. The index of excess air lambda is notoriously given by the quotient of a mass of air that is actually available for the combustion of a predetermined mass of fuel, in the numerator, and of a mass of air necessary for a stoichiometric combustion of this mass of fuel in the denominator. While internal combustion engines are operated with lambda values greater than 1 for optimum fuel economy, an optimized operation for the conversion of harmful substances into a three-way catalyst takes place with lambda = 1, and operation of the Internal combustion engine optimized at maximum power takes place with lambda values which are slightly lower than 1, for example with lambda = 0.9. In idle operation and in the partial load range close to idle operation, modern internal combustion engines are operated with lambda <1 or with lambda = 1. This means that there is naturally a certain reserve of lambda and torque available which it can be called up by adjusting the lambda to lambda = 0.9. For an estimate of the effect of such an enrichment it can be assumed that an enrichment of 10%, therefore an enrichment from for example lambda = 1 to lambda = 0.9, generates about 3% up to 5% more than couple. Contrary to the reserve of ignition angle and torque, this reserve of lambda and torque is not linked to a fuel penalty, so it is not linked to greater fuel consumption. Since the intervention on the lambda takes place with a speed similar to that of the intervention on the ignition angle, the additional use of an intervention on the lambda for torque adjustment allows a reduction of the ignition angle and torque reserve. and therefore a reduction in the greater fuel consumption. Other advantages can be deduced from the accompanying description and figures.

It is evident that the characteristics mentioned above and those still to be illustrated hereinafter can be used not only in the combination indicated each time, but also in other combinations, or individually, without abandoning the scope of the present invention.

Brief description of the drawings

Examples of embodiments of the invention are shown in the drawings and are illustrated in more detail in the following description. From time to time in schematic form the figures show:

Figure 1 an internal combustion engine with actuators, sensors and a control apparatus which is designed to manage the carrying out of configurations of the method according to the invention;

figure 2 a system structure of the control unit of figure 1,

figure 3 time curves of a nominal torque and of control variables m an example of embodiment of a method according to the invention; and figure 4 a flow chart as an example of embodiment of a process according to the invention.

Embodiments of the invention

Figure 1 shows an internal combustion engine 10 comprising at least one combustion chamber 12 which is hermetically sealed by a movable piston 14. The combustion chamber 12 is filled by means of an intake system 16 with air, or with a mixture of fuel and air. The fillings of the combustion chamber 12 are ignited by a spark plug 18. The exhaust gases from the burnt fillings of the combustion chamber are discharged via an exhaust gas system 20. The periodic switching from one filling to the other of the combustion chamber combustion is managed by at least one inlet valve 22 and an exhaust valve 24 which, in the representation of Figure 1, are operated by associated camshafts 26 and 28 in synchronism with a movement of the piston 14. The mass of the air which flows into the combustion chamber 12 is defined by the opening angle of a throttle valve 30. An air mass meter 32 serves to detect the mass of air flowing into the internal combustion engine 10.

To produce a fuel / air mixture capable of burning to the flowing air, fuel is added via an injector 34 or 36. The injector 34 is arranged in the intake system 16 and doses the fuel, in a configuration, upstream of a valve disc of the inlet valve 22. This type of fuel metering is also called injection into the intake pipe. As an alternative to injection into the intake pipe with such an injector 34, an injector 36 can also be provided which doses the fuel directly into at least a single combustion chamber 12, which is also called direct injection. In both alternatives the injector 34 or the injector 36 are actuated by a control device 33 with injection pulse widths ti. Each injector 34 or 36 is connected to a fuel pressure accumulator (not shown) and opens, during an injection pulse width ti, a passage section through which fuel is metered when the pulse width is applied. injection ti.

The position of the throttle valve 30 is set by the control unit 33 by actuating a throttle valve controller 38 with a control signal S_DK. The control device 33 further initiates combustion by activating the spark plug 18 with an ignition signal zw. The mass of the fuel / air mixture enclosed in the combustion chamber 12 before a combustion, the composition of fuel and air of this and the instant of ignition, or ignition angle substantially determine the energy transmitted to the piston 14 and therefore the internal torque of the internal combustion engine 10. The ignition angle zw, the injection pulse amplitudes ti and the control signals S_DK are therefore essential control variables for setting a required torque of the internal combustion engine 10.

To form this and other control variables, the control unit 33 processes signals m1 with respect to the mass of air flowing into the internal combustion engine 10, a signal FW, which characterizes a torque demand of a driver, a signal KWW, which represents an angular position of a crankshaft and therefore of the piston 14 of the internal combustion engine 10, a signal NWW, which represents an angular position of one of the camshafts 26 or 28, and a lambda signal, which is a measure for the composition of the fuel / air mixture burned in the combustion chambers 12. In this regard, the signal is provided to me by the air mass meter 32. A driver request transducer 40 detects the position of an accelerator pedal 42 and therefore provides the driver request signal FW. A crankshaft angle sensor 44 scans markings 46 of a translator wheel 48, rotationally coupled with the crankshaft, and provides the KWW signal. The NWW signal is provided by a crankshaft angle sensor. camshaft 50. An exhaust gas sensor 52 in the exhaust gas system 20 of the internal combustion engine 10 provides a measurement for the lambda air excess index.

The control device 33 of the internal combustion engine 10 is designed, in particular, it is programmed to regulate an effective torque of the internal combustion engine 10 by means of interventions on the ignition angle taking place in an ignition section 52, therefore interventions on the ignition angle zw, and through interventions on the filling taking place in a filling section * 54, for example interventions on the opening angle of the butterfly valve 30, on a variable nominal value T_soll. In this regard, the control apparatus 33 operates the internal combustion engine 10, in a configuration, with increased filling of the combustion chamber and with suboptimal ignition angles zw, therefore with a reserve of ignition angle and torque which allows an increase in torque from one ignition to the next ignition. The control unit 33 is also designed to regulate the effective torque of the internal combustion engine 10 additionally by means of interventions on the lambda which take place in a section of the fuel 26. The intervention on the lambda preferably takes place via an enrichment, therefore by means of a magnification of an injection pulse width ti, the magnification being a function of the torque requirement of the internal combustion engine 10.

Figure 2 shows a system structure of the control unit 33 of Figure 1. The control unit 33 can be divided, from the point of view of its operation, into a first block 58 and into further blocks 60, 62 '> 64. Block 58 is used to treat and process the input signals adduced. In the representation of figure 2 these are the signals KWW, NWW, FW, mi and lambda illustrated in relation to figure 1.

In a preferred configuration, in block 58 the formation of a nominal torque pipo and the division of the nominal torque Tesoli on the ignition section 52, on the filling section 54 and on the fuel section 56 take place, in stationary conditions, therefore with a request of constant torque, for example, the following subdivision occurs: to achieve a torque of x nm, an increasing intervention of, for example, a maximum of 1.08 is required by the filling section 54. xMm, a neutral intervention 1 is required from the fuel section 56. xNm and a 1: 1.08 reducing action is required from the ignition section 52. xNm. These requests are converted by blocks 60, 62 and 64 into corresponding control variables S_DK in the air section 54, ti in the fuel section 56 and zw in the ignition section 52. A filling is then set via the filling section 54 of the combustion chamber 12 which, with an optimal firing angle, will provide 8% more torque than is necessary for stationary operation. At the same time, a suboptimal firing angle zw is set via the ignition section. Compared to the torque with an optimal firing angle, only 1: 1.08 times the optimal torque is generated with the suboptimal firing angle. With the interaction of the air section 54 and the ignition section 52, 1.08: 1.08 times the desired torque is therefore obtained with an ignition angle and torque reserve of 8%.

In the presence of a torque request that changes, a modified subdivision of the torque requests takes place in blocks 60, 62, 64, respectively in the filling section 54, in the fuel section 56 and in the ignition section 52. change is divided into fast and slow parts. Slowly changing part dimensions are adjusted via fill run 54 and fast changing part dimensions are adjusted via runs 52 and 56 synchronized with the crank angle. An example for a portion that changes slowly is represented by the integral portion of an idle speed regulation, while proportional and / or differential portion shares of such an idle speed regulation are examples of part odds that change rapidly. Figure 3 shows curves related to time t of a variable nominal torque T__soll and of adjustment quantities in an example of embodiment of a method according to the invention. In this regard, figure 3a shows the curve of a nominal torque T_soll which in an instant tl suddenly passes from a first nominal value T_solll to a second higher nominal value T_soll2. Such a jump in the torque demand occurs, for example, in the case of an idle speed adjustment in the presence of an additional load to be supplied by the engine. A typical example is the insertion of a compressor in the air conditioning system. In the case of figure 3a, the difference T_soll between the new nominal value T__soll2 and the old nominal value T_solll exceeds a threshold value S. of operation at idle, then divides the increased torque demand, with time curves, on the ignition section 52, on the fuel section 56 and on the air section 54, which is qualitatively represented in figures 3b - d.

In this regard, a portion P of the adjustment of the number of idling revolutions is divided on the two sections 52 and 56 synchronized with the crank angle. In this regard, the change of the control variable in the ignition section 52 takes place at the instant tl in the representation of Figure 3, still a little more rapidly than the change of the control variable in the fuel section 56, at the instant t2, since the formation of the mixture must necessarily take place, by means of an injection pulse width ti, always a few degrees of crank angle before ignition. However, it is essential that a certain portion dT (lambda) can be made available in the fuel section 56. The portion dT (zw) of the modification of the torque that is created through the ignition section 52 can as a result be less than what would happen without an intervention in the treatment of fuel 56.

By means of the preceding comparison between the required variation of the nominal value dT_soll and the threshold value S it is ensured that the interventions on the lambda in the fuel section 56 take place only when the increases in the nominal value dT_soll are greater than the available torque reserve. Due to the fact that the torque reserve of the ignition section 52 is used first and that interventions on the fuel section 56 only take place when there is dT_soll> S, small variations in the torque dT_soll are compensated for by the ignition angle and torque reserve. , which positively affects fuel consumption. Intervention in the ignition section 52 improves efficiency. The intervention in the direction of enrichment in the fuel section 56, which in itself worsens the efficiency, is limited to the necessary cases, in which the required variation dT_soll of the nominal value of the torque T_soll exceeds the threshold value S.

Figure 3d shows the time curve of the intervention on the filling section 54. In the configuration shown, the filling section 54 takes over the integral part of an adjustment of the number of revolutions of operation at minimum. Through the filling section 54, through which the base torque T_basis is made available, an increase in the torque of the internal combustion engine 10 takes place in succession starting from the instant tl until, at the instant t3, it is added the new nominal torque T_soìl2 required. Parallel to the increase in the basic torque T_basis, which is made available through the filling section 54 between the instants tl and t3, the dT (zw) and dT (lambda) torque values set in the sections 52 and 56 can be reduced synchronized with the crank angle. Figure 3 therefore shows especially a process which, to increases in the nominal value, Tesoli reacts with a relatively rapid reduction of the torque reserve through the abrupt increase of dT (zw) and with a relatively slow variation of the filling, respectively of the base torque T_basis, whereby the torque reserve is again increased as the effect of the fill variation increases. At the instant t3, the intervention dT (zw) in the section of the ignition angle 52 has again fallen to its neutral value, so that the entire torque reserve is again available.

The magnitude of the threshold value S corresponds in this configuration to the maximum value of dT (zw). As a result of this division, it is ensured that the torque reserve is available again for new variations of the nominal value after a certain transitory time of the filling section 54.

In a preferred configuration, the method is used when the internal combustion engine 10 is operated at idle and / or in a range of revolutions and / or nominal torque close to the minimum with the torque reserve. The fuel shortage of the torque reserve is subsequently limited in these ranges.

The factor 1.08 mentioned for this configuration represents, in a preferred configuration, a lower limit for the ignition angle and torque reserve. In order to minimize the defect in terms of fuel of the intervention in the fuel section 56, the maximum interval is limited so that the resulting lambda values are in any case higher than lambda = 0.9. As a result, the presence of hydrocarbon emissions is also limited. in combination with the gradual taking charge of the intervention on the pair from PArte of the filling section, respectively by the base pair TJoasis set in the filling section 54, the duration of the time during which an enrichment takes place is also limited. itself disadvantageous for consumption and emissions.

Figure 4 shows an example of an embodiment of a method according to the invention in combination with an idle speed control LLR which is started in step 68. In step 70, a control deviation takes place. dn as the difference between a nominal value of the number of revolutions n_soll and an actual value of the number of revolutions n_ist. The actual value of the number of revolutions n_ìst can for example be formed as a time derivative of the crank angle signal KWW of the crank angle sensor 44 of Figure 1. In order to reduce a positive dn, the torque must be increased. generated by the internal combustion engine 10. For this purpose, in step 72 the formation of a variation dT_soll in the form of function ffdn ,, ..) takes place. The comma and the points in argument of t mean that t can depend on other operating parameters. In step 74 the dT_soll formed in step 72 is compared with the threshold value S. As soon as the threshold value S is not exceeded upwards, the torque demand in step 76 is satisfied by interventions on the rapid ignition section 52 , synchronized with the crank angle, and on the slow filling section 54. For this purpose, step 76 provides for the formation of an ignition angle zw in the form of function fl (dT) and the formation of a throttle valve regulation signal S_DK in the form of function f2 (dT). If, on the other hand, the threshold value S is exceeded upwards in phase 74, the program passes to phase 78, in which, in addition to the formation of ZW and S_DK, the formation of an intervention in the fuel section 56 takes place, at which the injection pulse amplitude ti is formed in the form of function f3 (dT). S__DK and ZW can be formed in step 78 with the same functions f2 (dT) and f1 (dT) used in step 76.

Insofar as it has been described so far of, lambda interventions are used in addition to ignition interventions in an internal combustion engine which, at certain operating points, works with a reserve of ignition angle and torque. An example of such a duty point is the duty range of an active idle regulation.

In one configuration, the adjustment of the torque through interventions on the lambda which take place in the fuel section (56) can completely or partially replace the interventions on the ignition angle which take place in the ignition section. In other words: the additional possibility of increasing the torque by means of an intervention on the lambda is exploited in order to adjust the duty point of the internal combustion engine so that the reserve of ignition angle and torque is as small as possible. In other configurations dT (zw) can be equal to zero at one operating point, in addition or at all operating points of the internal combustion engine, so that the internal combustion engine, at such an operating point, works with a torque adjustment synchronized with the crank angle and with an additional intervention on the air section or on the filling section.

Another configuration provides that interventions reducing the torque are carried out first of all in the fuel section and that a worsening of an efficiency of the ignition angle due to an intervention on the ignition that takes place in the ignition section (52) takes place only when an adjustment range of the intervention on the lambda is not sufficient to obtain a desired reduction in torque. In the fuel section, the reduction in torque can be obtained by increasing the lambda value, therefore by means of an impoverishment of the fuel / air mixture.

Claims (1)

Claims 1 .Procedure for regulating an effective torque of an internal combustion engine (10) to a variable nominal value (T_soll) by means of interventions on the ignition angle that take place in an ignition section (52) and by means of interventions on filling which take place in a filling section (54), characterized by the fact that the torque regulation also takes place through interventions on the lambda which take place in a fuel section (56). 2. Process according to claim 1, characterized in that the adjustment of the torque by means of interventions on the lambda which take place in the fuel section (56) completely or partially replaces the interventions on the ignition angle which take place in the ignition section. 3. Process according to claim 1 or 2, characterized by the fact that interventions reducing the torque are carried out first of all in the fuel section and by the fact that a worsening of an efficiency of the ignition angle due to an intervention on the ignition that takes place in the ignition section (52} it takes place only when an intervention adjustment interval on the lambda is not sufficient to achieve a desired reduction in torque. Process according to one of the preceding claims, characterized in that the internal combustion engine (10) is operated with an ignition angle and torque reserve which allows an increase in torque from one ignition to the next ignition. Method according to one of the preceding claims, characterized in that an increase in the nominal value (T_soll) reacts with a relatively rapid reduction of the torque reserve and a relatively slow modification of the filling, whereby the torque reserve is again increased as the effect of the fill modification increases. Method according to claim 5, characterized in that increases in the nominal value are compared with the available torque reserve and in that the intervention on the lambda only takes place when the increases in the nominal value are greater than the torque reserve which is available. Method according to one of the preceding claims, characterized in that the internal combustion engine (10) is operated with the torque reserve when idling and / or in a range of speeds and / or nominal torque close to idle, 8. Process according to claim 7, characterized in that the internal combustion engine (10) is operated with the torque reserve when its idling speed is adjusted. 9. Process according to claim 8, characterized by the fact that proportional and / or differential shares of the regulation of the number of revolutions of operation at idle are carried out through interventions on the ignition and / or interventions on the lambda, and by the fact that a quota an integral part of the regulation of the number of revolutions of operation at idle is carried out through interventions on the filling. 10. Process according to one of the preceding claims, characterized in that a maximum value of the torque reserve is less than or equal to 0.08 times a value of the torque that occurs for a given charge and with values for the lambda and for the '' optimum ignition angle from the point of view of torque delivery. Method according to one of the preceding claims, characterized in that the interventions on the lambdas in the fuel section (56) are limited so that the resulting lambda values are higher than 0.9. 12.Control device (33) of an internal combustion engine (10) which is designed to regulate an effective torque of the internal combustion engine (10) to a variable nominal value (Tesoli) by interventions on the ignition angle, which take place in an ignition section (52), and through filling interventions that take place on a filling section (54), characterized in that the control unit (33) is designed in such a way as to regulate the effective torque by means of in addition, interventions on the lambda which take place in a fuel section (56). Control device (33) according to claim 4, characterized in that it is designed in such a way as to manage the execution of a method according to one of claims 2 to 3.