GB2351816A

GB2351816A - Controlling multi-phase fuel injection in an internal combustion engine

Info

Publication number: GB2351816A
Application number: GB0016183A
Authority: GB
Inventors: Andreas Pfaeffle; Martin Grosser; Ruediger Fehrmann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-07-08
Filing date: 2000-06-30
Publication date: 2001-01-10
Anticipated expiration: 2020-06-30
Also published as: JP4347997B2; JP2001032742A; DE19931823A1; GB2351816B; GB0016183D0; DE19931823B4

Abstract

A method of determining fuel injection drive control values for an internal combustion engine, in which injection is divided into at least a first injection phase and a second injection phase. As described, for a three-phase system having preliminary (V), main (H) and further (N) injections, drive control durations (VE, HE, NE) for an electrically actuable valve 30 are determined 201, 202, 203, starting from a quantity of fuel to be injected (QVE, QHE, QNE) in each phase. Correction values (KNE, KHE. KVE) for the correction of the drive control durations are then determined starting from a basic correction value (K), the correction values for each injection phase being determined using different weighting factors (WN, WH, WV). The drive control duration values are then corrected 211, 212, 213 by the respective weighted correction values to obtain corrected duration values (VEX, HEX, NEK). The weighting factors may be different for each phase, and may depend on the operational state of the engine.

Description

2351816 FUEL INJECTION CONTROL IN AN INTERNAL COMBUSTION ENGINE The

present invention relates to a method and determining means for determining fuel injection control values for an internal combustion.

In DE 43 12 586 there are described a method and a device for the control of a fueladmetering system of an internal combustion engine in which the drive control of at least one electrically actuated valve determines the quantity of fuel to be injected. In certain operational states there is ascertained a minimum drive control duration just sufficient for fuel to be injected. For this purpose, the drive control duration for a preliminary injection phase is either increased or reduced starting from a starting value. When a change in a signal occurs, such as to indicate that injection has taken place, then the instantaneous drive control duration is stored as minimum drive control duration and subsequently used for correction of the drive control duration.

A further method and device for control of an internal combustion engine are known from DE-OS 39 29 747 (US 50 70 836), in which again a minimum drive control duration is determined. For this purpose, the duration of the preliminary injection phase is increased, starting from a value at which no injection takes place, until it is recognised from a reporting signal that a preliminary injection has taken place. The drive control pulses of the main injection are kept constant. The minimum drive durations are ascertained and stored individually for each cylinder and used in subsequent preliminary injection phases for correction of the drive control duration.

It is a disadvantage of this method that the correction values are ascertained merely for the preliminary injection phase and used for correction of the preliminary injection. Scatter, which has an effect on the main injection phase and any final supplementary injection phase, cannot be corrected by this method.

A further method and device for the control of an internal combustion engine are described in DE-OS 33 36 028, in which associated with each cylinder is a regulation process which sets the torque delivered by the individual cylinders to a common mean value. The regulators essentially contain an integral component, the value of which can be regarded as a correction value. A correction value can be ascertained by starting from this integral 2 value. It is a disadvantage that these correction values are or can be ascertained only in certain operational states and are used merely for the correction of the main injection.

There thus remains scope to reduce the tolerances of injection systems, especially those with common rail injection valves.

According to a first aspect of the present invention there is provided a method for the control of an internal combustion engine, in which the fuel injection is divisible into at least a first partial injection and a second partial injection, a drive control duration for an electrically actuable valve is presettable starting out from the quantity of fuel to be injected and at least one correction value for the correction of the drive control duration is determined, characterised in that correction values for all partial injections are presettable starting from the correction value by different weighting.

Preferably, the partial injections comprise at least one of a main injection, a preliminary injection and a further injection. For preference the correction values for the different partial injections are weighted differently. The weighting factors for the different partial injections can be presettable in dependence on the operational state of the internal combustion engine.

According to a second aspect of the present invention there is provided a device for the control of an internal combustion engine, wherein the fuel injection is divisible into at least a first partial injection and a second partial injection and means are provided, which preset a drive control duration for an electrically actuable valve starting out from the quantity of fuel to be injected and which determine at least one correction value for the correction of the drive control duration, characterised in that means are provided, which preset correction values for all partial injections starting out from the correction value by different weighting.

According to a third aspect of the invention there is provided control means for controlling multi-phase fuel injection in an internal combustion engine, comprising means for determining a respective fuel injection quantity for each phase of the injection in dependence on at least one ascertained parameter, means for determining for each phase a respective drive control duration value for drivable injection fuel supply means, means for determining a basic correction value in dependence on the at least one parameter, 3 means for determining an individually weighted correction value for each duration value in dependence on the basic correction value, interlinking means for interlinking each duration value with the respective weighted correction value to derive a corrected duration value and means for applying the corrected duration values to the injection fuel supply means for driving thereof.

A method exemplifying and means embodying the invention may have the advantage by comparison with the state of the art that tolerances in the injection system can be significantly reduced. This reduction in tolerances has an effect on all injection phase,_ especially preliminary, main and final supplementary injection phases. In particular, tolerances due to ageing can be compensated for. It is particularly advantageous that system components can be used with greater tolerances, as correction can be made for the tolerances.

An example of the method and embodiment of the determining means of the invention will now be more particularly described by way of example with reference to the accompanying drawings, in which Fig. 1 is a schematic block diagram of a fuel admetering system of an internal combustion engine, and Fig. 2 is a block diagram of determining means embodying the invention.

Referring now to the drawings, there is shown in Fig. 1 the significant elements of a fuel admetering system of an internal combustion engine. The engine 10 has a specific quantity of fuel admetered to it by a fueladmetering unit 30 at a specific instant. Different sensors 40 detect measurement values 15 characterising the operational state of the engine and supply these to a control device 20. In addition, different output signals 25 of further sensors 45 are supplied to the control device 20. These further sensors detect magnitudes which characterise the state of the fuel-admetering unit and/or environmental conditions. Such a magnitude can be, for example, the wish of a driver of a vehicle fitted with the engine. The control device 20, starting from the measurement values 15 and the further magnitudes 25, computes drive control pulses 35 acting on the unit 30.

4 Preferably, the engine 10 is a direct injection and/or compression ignition internal combustion engine. The fuel admetering unit 30 can take various forms, for example, it can be a distributor pump for which an electromagnetic valve determines the instant and/or duration of fuel injection. The fuel admetering unit can also have the form of a commonrail system, in which a pump compresses fuel in a storage device. From this storage device, fuel is supplied by way of injectors to the combustion chambers of the engine. The duration and/or the start of the injection is controlled by means of the injectors. In that case, each injector preferably comprises an electromagnetic valve or a piezo- electric actuator.

A respective electrically actuable valve is provided for each cylinder. In the following, the term electrically actuable valve is used to embrace electromagnetic valves and/or the piezo-electric actuators.

The control device 20 can compute a quantity of fuel, which is to be injected into the engine, in known manner. This computation takes place in dependence on different measurement values 15, such as for example engine rotational speed, engine temperature, actual start of injection and possibly further magnitudes characterising the operational state or environment of the vehicle. These further magnitudes are, for example, the setting of the vehicle accelerator pedal or the pressure and the temperature of the ambient air. Moreover, it can be the case that a desired torque is preset by other control units, for example, a transmission control, and is converted into a fuel quantity signal.

The control device 20 then converts the desired quantity of fuel into the drive control pulses 35 to act on a quantity determining member of the fuel admetering unit 30. The electrically actuated valve serves as the quantity determining member. This electrically actuated valve is arranged so that the quantity of fuel to be injected is determined by the opening duration or the closing duration of the valve.

Frequently, a small quantity of fuel is admetered shortly before a main injection into the cylinder, whereby the noise behaviour of the engine can be substantially improved. This injection is termed preliminary injection phase and the subsequent actual injection as main injection phase. Moreover, a small quantity of fuel can be admetered after the main injection phase. This is then denoted as a further injection phase. In addition, the three phases can themselves be subdivided into further phases, i.e. the main, the preliminary and/or the further injection phases can each be divided up into sub-phases.

A problem with such fuel admetering systems is that the electrically actuated valves can admeter different quantities of fuel for the same drive control signal. In particular, the drive control duration which is just sufficient for fuel to be admetered depends on different factors. This minimum drive control duration, also termed ADO, leads to an injection, whereas durations smaller than the minimum duration do not lead to injection. The minimum duration depends on different factors, such as temperature, fuel type, service life and further influences. In order to be able to achieve an accurate fuel admetering of fuel, this minimum drive control duration must be known.

The minimum drive control duration is usually ascertained in specific operational states for an injection phase and used for correction of the following like phases. In the case of phases for which no correction values are or can be ascertained, no correction takes place.

In a method exemplifying the invention, however, correction values are ascertained and used for all injection phases. It is particularly advantageous if the correction value is weighted differently for the individual phases and if the correction value is predetermined in dependence on the operational state of the engine. The operational state of the engine is determined by reference to, in particular, the engine rotational speed and/or a load magnitude and/or a torque magnitude and/or a magnitude characterising the quantity of fuel to be injected.

The quantity of fuel to be injected can be the quantity for the main injection phase or the entire quantity injected, i.e. the sum of the preliminary, main and further injection phases. The drive control duration can also be used in place of the quantity of fuel.

The procedure is particularly advantageous when the injection phases are divided up into further partial phases. Thus, for example, the main phases can be divided up into two or more partial phases. A corresponding procedure can apply to the further and preliminary injection phases. It is also advantageous if the weighting of the correction values is predetermined in dependence on the operational state of the engine.

6 A method exemplifying and determining and control means embodying the invention are illustrated in Fig. 2, in which elements already described in Fig. 1 are denoted by corresponding reference symbols. The sensors 40 act on a quantity presetter 22 and a correction value presetter 24 as well as on a first weighting block 221, a second weighting block 222 and a third weighting block 223 by signals which characterise the operational state of the engine. These signals can be, in particular, the rotational speed n of the engine and a magnitude which characterises the quantity of fuel to be injected. This magnitude can be, for example, a load value andlor a torque value and is usually not detected by a sensor, but is preferably an internal magnitude of the control device 20.

In place of signals from the sensors 40, the output signals of the further sensors 45 can be supplied to the quantity presetter 22, the correction value presetter 24 and the weighting blocks 211 to 223.

The further elements illustrated in Fig. 2, in particular the presetters 20 and 22, are components of the control device 20.

The quantity presetter 22 passes a signal QVE, which corresponds with the quantity of fuel to be admetered during preliminary injection, to a first conversion block 201, a signal QHE, which corresponds with the quantity of fuel for the main injection, to a second conversion block 202 and a signal QNE, which corresponds with the quantity of fuel for the further injection, to a third conversion block 203. The first block 201 applies to a first input of an interlinking point 211 a signal VE which corresponds with the drive control duration for the preliminary injection, the second block 202 applies to a first input of a second interlinking point 212 a signal HE which corresponds with the drive control duration for the main injection and the third block 203 applies to a first input of a third interlinking point 213 a signal NE which corresponds with the drive control duration for the further injection.

An output signal KVE of the first weighting block 221 is applied to a second input of the interlinking point 211, an output signal KHE of the second weighting block 222 is applied to a second input of the interlinking point 212 and an output signal KNE of the third weighting block 223 is applied to a second input of the third interlinking point 213. The weighting blocks 221 to 223 are acted on by a correction value K, which is provided by the correction value presetter 224, and by the output signals of different sensors.

7 An output signal VEK, which corresponds with the corrected drive control duration for the preliminary injection, of the first interlinking point 211 is applied to the fuel-admetering unit 30, as are an output signal HEK of the second interlinking point 212, which corresponds with the corrected drive control duration for the main injection, and an output signal NEK of the third interlinking point 213, which corresponds with the corrected drive control duration for the further injection.

in Fig. 2 the method is illustrated by an example in which an injection in the combustion cycle is divided into three phases, namely preliminary injection, main injection and further injection, The method is not limited to this specific number of injection phases. It can be used for any desired number of phases, thus two phases or more than three phases. It is merely necessary to adapt the number of conversion blocks, interlinking points and weighting blocks to the number of the phases.

Starting out from the different engine operating characteristic magnitudes, the correction value presetter 24 ascertains correction values K by which the injection duration is to be corrected. These correction values are preferably stored permanently and for preference an individual correction value is stored for each cylinder. It is particularly advantageous if the correction values are stored in"dependence on the operational state of the engine. Preferably, the correction values are stored in dependence on the rotational speed value n and a load value.

The ascertaining of the correction values preferably takes place as described in the state of the art. Thus, for example, starting from a value of the drive control duration for which no injection takes place, the duration is increased until it is recognised by means of a reporting signal that injection takes place. The thus-ascertained duration for which injection just takes place is termed a minimum drive control duration. Proceeding from this minimum drive control duration, the correction value can then be ascertained. It is provided in the case of a simple example that the minimum drive control duration is equal to the correction value K.

Starting out from different engine operating characteristic magnitudes, the quantity presetter device 22 computes the signals QVIE, OHE and QNE, characterising the quantity of the preliminary injection, the main injection and the further injection. These quantity signals for the preliminary, main and further injection are converted in the first, second and 8 third conversion blocks 201 to 203 into drive control durations which determine the duration of the fuel injection for the preliminary main and further injection.

The drive control duration is preferably that for the electrically actuable valve of the fueladmetering unit 30. The drive control durations VE, HE and NE are in that case corrected by the correction value K at the respective interlinking point 211, 212 or 213. The correction can be effected, for example by adding the minimum drive control duration to the computed drive control duration. The thus-ascertained corrected drive control durations VEK for the preliminary injection, HEK for the main injection and NEK for the further injection are then applied to the fueladmetering unit 30.

Since tolerances and scatter have different effects on the individual injection phases, the correction values for the different phases are weighted differently. This takes place in the first, second and third weighting blocks. The thus-weighted correction values are then applied to the different interlinking points.

It is particularly advantageous if the weighting factors WN for the further injection, WH for the main injection and WV for the preliminary injection are predetermined in dependence on the engine operational state, in particular rotational speed and load.

The influence of the different cylinder counterpressures for the individual injection phases and/or the different operational states can thereby be taken into consideration. The cylinder counterpressure has a significant influence on the admetered quantity of fuel. For otherwise equal parameters, such as the drive control duration, smaller injected quantities result for higher cylinder counterpressures.

9

Claims

1 A method of determining fuel injection drive control values for an internal combustion engine in which injection in each combustion cycle is carried out in at least two phases, comprising the steps of determining for each injection phase a respective drive control duration value for an electrically operable fuel flow influencing valve in dependence on a quantity of fuel to be injected in that phase, determining respective correction values for the duration values for the phases by individually weighting a basic correction value and correcting the duration values by the respective correction values.

2. A method as claimed in claim 1, wherein one of the phases is a main injection phase.

3. A method as claimed in claim 1 or claim 2, wherein one of the phases is a preliminary additional injection phase.

4. A method as claimed in any one of the preceding claims, wherein one of the phases is a final additional injection phase.

5. A method as claimed in any one of the preceding claims, wherein the basic correction value is weighted differently for the phases.

6. A method as claimed in any one of the preceding claims, wherein the step of determining the correction values is carried out by weighting the basic correction value by weighting factors determined in dependence on the operational state of the engine.

7. A method as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

8. Determining means for determining fuel injection drive control values for an internal combustion engine in which injection in each combustion cycle is carried out in at least two phases, comprising means operable to determine for each injection phase a respective drive control duration value for an electrically operable fuel flow influencing valve in dependence on a quantity of fuel to be injected in that phase, to determine respective correction values for the duration values for the phases by individually weighting a basic correction value and to correct the duration values by the respective correction values.

9. Determining means substantially as hereinbefore described with reference to the accompanying drawings.

10. Control means for controlling multi-phase fuel injection in an internal combustion engine, comprising means for determining a respective fuel injection quantity for each phase of the injection in dependence on at least one ascertained parameter, means for -determining for each phase a respective drive control duration value for drivable injection fuel supply means, means for determining a basic correction value in dependence on the at least one parameter, means for determining an individually weighted correction value for each duration value in dependence on the basic correction value, interlinking means for interlinking each duration value with the respective weighted correction value to derive a corrected duration value and means for applying the corrected duration values to the injection fuel supply means for driving thereof.