EP0502849B1 - Electronic fuel-supply control system for an internal-combustion engine - Google Patents

Abstract

The system proposed includes means for determining a basic injection-quantity signal and a transitional compensation signal for regulating the measured amount of fuel when accelerating and decelerating. Depending on engine load and rpm, a cylinder-wall fuel-film signal and a control-factor signal (Tk) are generated, and the transitional compensation signal takes into account both the cylinder-wall fuel-film signal and the control-factor signal. The control-factor signal can either be extracted from a characteristic plot or be two discrete values. The system proposed gives optimum transitional behaviour as regards engine exhaust characteristics.

Description

The invention is based on an electronic control system for fuel metering in an internal combustion engine with sensors for load, speed and temperature, means for determining a basic injection quantity signal and a transition compensation signal for adapting the metered fuel quantity in the event of acceleration and deceleration according to the type of the main claim (compare US A-4 852 538).

. Dabei sind FM 1 drehzahl- und lastabhängig und FM 2 temperaturabhängig.A fuel metering system is known from DE-OS 30 42 246 and the corresponding US Pat. No. 4,440,136, in which an enrichment factor is formed according to a certain formula for acceleration enrichment and the individual components of the formula are retrievable from memories depending on the load and speed. The enrichment factor follows $\text{FM = 1 + FM 1 x <figure-callout id="2" label="FM" filenames="imgf0003.png" state="{{state}}">FM</figure-callout> 2}$

. FM 1 is speed and load dependent and FM 2 is temperature dependent.

DE-OS 36 23 041 and the corresponding US patent application SN 169 274 describe a method for metering fuel in the event of acceleration known that takes into account the temporal relationship between the occurrence of the acceleration request signal and the intake valve times, so that the required additional amount of fuel for realizing the acceleration request can be metered as optimally as possible. For this purpose, provision is made, inter alia, to distribute the calculated additional quantity of fuel over a number of successive metering processes or to provide so-called intermediate splashes.

The physical problem with acceleration enrichment is to provide the required additional quantity in the combustion chambers of the internal combustion engine itself. This is particularly difficult at low temperatures because part of the amount of fuel metered into the intake manifold then condenses on the walls of the intake manifold and is therefore ultimately not immediately available to the actual combustion process. The fuel depositing on the inner wall of the intake manifold forms a so-called fuel wall film. In addition to the design, it is primarily temperature, speed and load dependent. Since the assembly and disassembly of the fuel wall film in the case of non-stationary operating states of the internal combustion engine can only be controlled with great difficulty, different approaches for describing the wall film have become known in the literature. A basic work on this can be found in the SAE paper 810494 "Transient A / F Control Caracteristics of the 5 liter Central Fuel Injection Engine" by CF Aquino.

The object of the present invention is to provide an electronic control system for the fuel metering in an internal combustion engine, in which an optimal transition behavior with regard to exhaust gas is achieved during acceleration and deceleration processes.

Advantages in the invention

The control system for fuel metering according to the invention is characterized by good exhaust gas behavior in the transition mode, in that a transition compensation signal for adapting the metered fuel quantity in the event of acceleration and deceleration is processed, including a wall film quantity difference signal and a control factor signal, depending on the operating parameters.

Further advantages in the invention result in connection with the subclaims from the following description of exemplary embodiments.

drawing

Embodiments of the invention are described and explained in more detail in the drawing. 1 shows a rough overview diagram of an electronic control system for fuel metering in an internal combustion engine, FIG. 2 shows in block form the most important elements of an electronic control system for fuel metering in connection with the provision of a transition compensation signal, FIG. 3 shows a flow chart of a first possibility for forming a transition compensation signal, FIG. 4a shows a time diagram of this implementation, FIG. 4b shows a time diagram to show a further possibility of forming a transition compensation signal, and finally FIG. 5 shows a flow diagram to implement this second possibility of forming a transition compensation signal.

Description of the embodiments

Figure 1 shows a rough overview of an internal combustion engine with its most important sensors, a control unit and an injection valve. The internal combustion engine is designated 10. It has an air intake pipe 11 and an exhaust pipe 12. In the air intake pipe 11 there is a throttle valve 13, possibly an air quantity or air mass meter 14 and an injection valve 15 for metering the required amount of fuel into the air flow flowing to the internal combustion engine 10. A speed sensor is denoted by 16, a temperature sensor by 17. A load signal from a throttle valve sensor 18 and / or from the air quantity or air mass sensor 14, together with the signals from the other sensors, reaches a control unit 20, which has a control signal for the at least one injection valve 15 and possibly an ignition signal and other control signals essential for the internal combustion engine control.

The basic structure of a fuel metering system for an internal combustion engine shown in FIG. 1 is known. The invention is concerned with the problem of providing a transition compensation signal for the acceleration or deceleration case with the aim of achieving the best possible transition behavior of the internal combustion engine or the vehicle equipped therewith while the exhaust gas is as clean as possible.

A block diagram of the electronic control system according to the invention for fuel metering can be found in FIG. 2. There, elements already known from FIG. 1 are provided with the reference numbers already mentioned.

zwischen aufeinanderfolgenden Wandfilmmengenwerten.A basic map for emitting a basic injection signal tlk is designated by 25. A control factor map for delivering a control factor signal Tk bears the reference numeral 26 and 27 denotes a wall film quantity map for delivering a corresponding wall film quantity signal Wk. All three characteristic diagrams 25, 26 and 27 receive signals from the load sensor 17 and speed sensor 15 on the input side. The wall film quantity characteristic diagram 27 is followed by a difference-forming means for representing a differential signal $\text{Δ Wn = Wk - Wk-1}$

between successive wall film quantity values.

A block 30 emits a signal which marks the end of a pushing or pushing operation. A subsequent block 31 generates a correction signal TUKSAS depending on the previous duration of an overrun operating phase. An addition point 32 subsequently connects the output signals of the two blocks 29 and 31. A multiplier 33 follows, in which the output signal of the addition point 32 is multiplicatively linked with a temperature-dependent signal from a block 34, which is in turn connected to the temperature sensor 16. The result is then a wall film change signal Δ Wn corrected as a function of temperature and operating time.

zur Verfügung steht. Dieses Signal wird in einer Multiplikationsstelle 36 mit dem Signal Tk vom Absteuerfaktorkennfeld 26 verknüpft. Ausgangsseitig der Multiplikationsstelle 36 steht dann das Übergangskompensationssignal UKk zur Verfügung. Dieses Signal wird nachfolgend in einer Additionsstelle 37 mit dem Ausgangssignal tlk des Grundkennfeldes 25 verknüpft und anschließend in einem Block 38 ggf. noch lambdaabhängig und temperaturabhängig korrigiert. Das Ausgangssignal des Korrekturblocks 38 steht dann als Gesamteinspritzsignal ti letztlich dem Einspritzventil 14 zur Verfügung.In a subsequent block 29, the not yet injected remainder of all previous difference formations SUM Δ Wk-1 is added to the current change signal Δ Wn, with the result that a signal is output on the block 29 side $\text{SUM Δ Wk = Wk - Wk-1 + SUM Δ Wk-1}$

is available. This signal is combined in a multiplication point 36 with the signal Tk from the control factor map 26. The transition compensation signal UKk is then available on the output side of the multiplication point 36. This signal is subsequently linked in an addition point 37 to the output signal tlk of the basic characteristic map 25 and then corrected in a block 38, if necessary depending on the lambda and on the temperature. The output signal of the correction block 38 is then ultimately available to the injection valve 14 as a total injection signal ti.

Also to be mentioned is a difference-forming element 39 which receives both the signal on line 35 and the output signal of multiplication point 36 and which forms the second signal to be processed in block 29 one calculation step later.

The subject of FIG. 2 is expediently explained on the basis of a flow chart shown in FIG. The individual calculation steps can take place both in the time grid and in the angle grid (e.g. related to the crankshaft).

In Figure 3, the starting point is designated 40. A load value α k and a speed value nk are read in in block 41. The letter k clarifies the values of the individual variables available at time tk. With k-1 the corresponding values are designated at the previous sampling time.

Block 41 is followed by a block 42 in which a value for the basic metering signal tlk, for the wall film fuel quantity Wk and a control factor Tk are read out from the characteristic diagrams 25, 26 and 27 known from FIG. 2, or are already made available as interpolation values.

In block 43, corresponding to block 28 of FIG. 2, a difference is formed between the individual wall film fuel quantity values at successive sampling times. In block 44, a correction takes place depending on the temperature and the duration of the overrun. In addition to this value Δ Wn formed in block 44, the remainder of the previous difference SUM Δ Wk-1, which has not yet been injected, is added to the current wall film difference Δ Wn in the following block 45. The subsequent block 46 corresponds to the multiplication point 36 of FIG. 2. In it, the value of the currently applicable transition compensation signal UKk is determined. It follows in block 47 the calculation of a change amount of SUM Δ Wk for the next calculation step known from the difference formation point 39 in FIG. 2 in block 45. Finally, in block 48 the output signal is formed in accordance with the addition point 37 in FIG. 2, which further corrections can follow in block 49. A signal relating to the total injection period ti total is then output and the program run ends with the program step Stop (50).

The objects of FIGS. 2 and 3 thus disclose a load-dependent and speed-dependent reading of a wall film fuel quantity signal from a corresponding characteristic diagram 27 or 42 at a sampling time tk. This wall film fuel quantity value is redetermined at each sampling time depending on the load and speed and a difference is determined therefrom. This is followed by taking into account the residual values of previous wall film differences with blocks 29 and 44 respectively. Depending on the duration of the preceding overrun operation or the prevailing temperature, correction terms are then formed, which ultimately result in a wall film fuel quantity signal SUM ΔWk on line 35 or in block 47. At this value, a control factor signal Tk from the control factor map 26 or 42 is taken into account multiplicatively for the formation of a current applicable transition compensation signal UKk and this transition compensation signal UKk is added to the basic injection quantity signal tlk from the basic map 25.

With this signal, the applicable wall film quantity value is continuously determined and changes in formation are taken into account as a transition compensation signal.

FIG. 4a shows an example of the course of the transition compensation (UK) as it results from the function described in FIGS. 2) and 3). An acceleration request should occur at time to. The time course of the transition compensation is determined by the throttle valve and speed-dependent control factor T.

FIG. 4b shows a typical course when the transition compensation is implemented differently. Immediately after the necessary transition compensation has been calculated, a so-called intermediate spray is triggered, which provides an additional quantity of fuel asynchronously to the normal injection. The remaining excess amount is divided into two stores. At time t 1, the exponential reduction of this memory begins, with one memory being driven quickly and the other slowly. From the time t₂ only slow slowdown takes effect. The course from FIG. 4b makes it possible to dispense with the calculation of the control factor from a characteristic diagram. Instead, the map is replaced by 2 control factors, which are derived from 2 applicable constants. In order to make the allocation to fast and slow storage variable at different speed / load points, the distribution factor can also be described by a map of speed and load.

FIG. 5 shows a possible implementation of the signal curve in FIG. 4b. Blocks which correspond to those in FIG. 3 are also provided with the corresponding reference numbers. It can be seen that in block 22 the formation of a control factor signal from a map does not take place and this factor is specifically formed in the further course.

Following the block 43 known from FIG. 3 regarding the formation of a current wall film difference signal Δ Wn, this difference signal is queried for a threshold.

${\text{SUM Δ Wk}}_{\text{S}}{\text{= Δ Wn.A}}_{\text{S}}{\text{+ SUM Δ Wk-1}}_{\text{S}}$

${\text{mit A}}_{\text{L}}{\text{+ A}}_{\text{S}}\text{= 1}$

Wird in Block 55 auf ein Änderungssignal größer als ein bestimmter Schwellwert erkannt, dann ergibt sich eine Berechnung in Block 57 nach den folgenden angegebenen Formeln

${\text{SUM Δ Wk}}_{\text{L}}{\text{= Δ Wn.A}}_{\text{L}}{\text{+ SUM Δ Wk-1}}_{\text{L}}$

${\text{SUM Δ Wk}}_{\text{S}}{\text{= Δ Wn.A}}_{\text{S}}{\text{+ SUM Δ Wk-1}}_{\text{S}}$

${\text{SUM Δ WK}}_{\text{Z}}{\text{= Δ Wn.A}}_{\text{Z}}$

${\text{mit A}}_{\text{L}}{\text{+ A}}_{\text{S}}{\text{+ A}}_{\text{Z}}\text{= 1}$

A_L, A_S und A_Z sind applizierbare Faktoren, welche die gesamte neu hinzugekommene Wandfilmdifferenz Δ Wn auf die drei Speicher Langzeit-, Kurzzeit- und Zwischenspritzerspeicher aufteilt.This query is marked with 55. If the threshold is not reached, change values are calculated in a block 56 according to the formulas

${\text{SUM Δ Wk}}_{\text{L}}{\text{= Δ Wn.A}}_{\text{L}}{\text{+ SUM Δ Wk-1}}_{\text{L}}$

${\text{SUM Δ Wk}}_{\text{S}}{\text{= Δ Wn.A}}_{\text{S}}{\text{+ SUM Δ Wk-1}}_{\text{S}}$

${\text{with A}}_{\text{L}}{\text{+ A}}_{\text{S}}\text{= 1}$

If a change signal greater than a certain threshold value is detected in block 55, then a calculation in block 57 results according to the following formulas

${\text{SUM Δ Wk}}_{\text{L}}{\text{= Δ Wn.A}}_{\text{L}}{\text{+ SUM Δ Wk-1}}_{\text{L}}$

${\text{SUM Δ Wk}}_{\text{S}}{\text{= Δ Wn.A}}_{\text{S}}{\text{+ SUM Δ Wk-1}}_{\text{S}}$

${\text{SUM Δ WK}}_{\text{Z.}}{\text{= Δ Wn.A}}_{\text{Z.}}$

${\text{with A}}_{\text{L}}{\text{+ A}}_{\text{S}}{\text{+ A}}_{\text{Z.}}\text{= 1}$

A _L , A _S and A _Z are applicable factors which divide the total newly added wall film difference Δ Wn into the three long-term, short-term and intermediate-spatter stores.

). Wird im folgenden in einer Abfrageeinheit 59 eine positive Änderung des Drosselklappensignals erkannt, erfolgt in Block 60 die Ausgabe eines Zwischenspritzers (UKK_Z). Nach Ausgabe dieses Zwischenspritzers wird das entsprechende Zwischenspritzersignal UKK_Z in Block 61 auf Null gesetzt. Eine programmäßige Vereinigungsstelle 62 verbindet die Ausgänge der beiden Blöcke 56 und 61 sowie der Abfrageeinheit 59 bezüglich des Ausgangs "Änderung der Drosselklappenposition negativ".This is followed by a block 58 for forming an intermediate sprayer signal ( ${\text{UKK}}_{\text{Z.}}\text{= SUM Δ Tool}$

). If a positive change in the throttle valve signal is subsequently detected in an interrogation unit 59, an intermediate sprayer (UKK _Z ) is output in block 60. After this intermediate sprayer has been output, the corresponding intermediate sprayer signal UKK _Z is set to zero in block 61. A programmatic union 62 connects the outputs of the two blocks 56 and 61 and the interrogation unit 59 with respect to the output "change in throttle valve position negative".

For all branches together, the calculation of the slow down-control (T _L ) and the fast down-control (T _S ) is carried out in block 46 '. This is followed by a block 65 which converts the transition compensation signals UKK _L or UKK _S to applicable maximum values. UK _S and max. UK _L limited. According to the flow chart of FIG. 3, a block 47 follows, which in turn is followed by a block 66 for forming an overall injection time signal.

In view of the fact that, depending on the transition compensation signal, the total injection signal tik can also assume negative values, a query 67 follows a threshold greater or less than 0. If the total injection signal is less than 0, the injection time is limited to 0 in a block 68 and at the same time the negative The rest is taken into account for the next injection.

If the value formed in block 66 is greater than 0, the entire injection signal can be metered in without a certain residual value having to be taken into account in the subsequent injection. This is reflected in block 70. Ultimately, further corrections are made in block 49 and the resulting injection quantity signal ti total is output.

4b is the fact that changes in the wall film quantity in blocks 56 and 57 are weighted with values A _L , A _S and additionally A _Z with the aim of curtailment with different time constants as shown in FIG. 4a.

Claims (12)

1. Electronic control system for fuel metering in an internal combustion engine, with sensors for load (α, p, QL), rotational speed and temperature, means for determining a basic injection-quantity signal, and an additive transition compensation signal for adapting the fuel quantity metered in in the case of acceleration and deceleration, in which, for transition compensation, a wall-film quantity alteration signal SUM ΔWk, in the form of an overall balance comprising the alterations in the operating point-dependent wall-film quantity signal, and a discharge factor signal (Tk) are formed as a function of load and rotational speed and in which the transition compensation signal UKk is dependent on the wall-film quantity alteration signal SUM ΔWk and on the discharge factor signal (Tk) characterised in that the overall balance also takes into account the already ejected partial quantities.
2. Electronic control system according to Claim 1, characterised in that the transition compensation signal UKk is obtained from a multiplication of the wall-film quantity alteration signal SUM ΔWk and the discharge factor (Tk).
3. Electronic control system according to Claim 1, characterised in that the wall-film quantity alteration signal is formed in accordance with the following formula:
   
   $\text{SUM ΔWk = Wk - Wk-1 + SUM Wk-1, where Wk = f(loadk, nk).}$

   
4. Electronic control system according to Claim 3, characterised in that SUM ΔWk can be corrected as a function of the temperature (Θ) and overrun duration.
5. Electronic control system according to Claim 1, characterised in that the discharge factor signal (Tk) is dependent on the load and rotational speed ( $\text{Tk = f (loadk, nk)}$

   

   ).
6. Electronic control system according to one of Claims 1 to 5, characterised in that when determining the transition compensation signal for the subsequent fuel metering signal, the portion already metered in is taken into account in accordance with the following formula:
   
   $\text{SUM ΔWk-1 = SUM ΔWk - UKk.}$

   
7. Electronic control system according to Claim 1 or 5, characterised in that the discharge factor signal (Tk) is dependent on the sign of the load change.
8. Electronic control system according to Claim 1, 5 or 7, characterised in that the wall-film quantity difference signal SUM ΔWk is distributed in each step between two storage devices and one storage device is discharged rapidly (using Ts [sic]) and the other storage device is discharged slowly (using Tl [sic]).
9. Electronic control system according to Claim 1, 5 or 7, characterised in that the wall-film quantity difference signal SUM ΔWk is distributed in each step between three storage devices and one storage device is always completely emptied in one step (interim injection storage device) and the other two are discharged rapidly (using Ts [sic)) and slowly (using Tl [sic]) respectively.
10. Electronic control system according to Claim 8 or 9, characterised in that the factors for the distribution of the wall-film quantity alteration signal (SUM ΔWk) between the various storage devices are not constant but are predetermined in the form of a characteristic map against rotational speed and load.
11. Electronic control system according to one of Claims 1 to 8, characterised in that the transition compensation signal (UKk) can be limited.
12. Electronic control system according to one of Claims 1 to 9, characterised in that, in the case of a calculated injection time of less than zero, no fuel is metered in at the next metering instant and the negative residual amount is taken into account in the following metering process.

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