DE102012205839A1 - Method for operating fuel injector of internal combustion engine e.g. diesel engine, involves determining injection operation request not within injection prohibited request area by decreasing or increasing target injection request - Google Patents

Abstract

The method involves establishing injection prohibited request areas. A target injection request is set. An injection operation request which is not within the injection prohibited request area is determined by decreasing or increasing the target injection request, when the target injection request falls within the injection prohibited request area. The fuel injectors (18) of an internal combustion engine (10) are driven according to the injection operation request. Independent claims are included for the following: (1) processing unit; and (2) computer program stored in machine-readable storage medium for operating injector of internal combustion engine.

Description

The present invention relates to a method for operating at least one injector and a computing unit for its implementation.

State of the art

Petrol or diesel internal combustion engines, in which the fuel is injected directly by means of injectors in the combustion chambers, are advantageous in terms of efficiency, emission behavior and power output. In order to exploit the advantages of this so-called direct injection, high demands are to be met on the accuracy of the injection. This applies in particular to so-called spray-guided combustion processes and / or small fuel quantities.

The metering of small amounts of fuel is required especially for multiple injections, the start and warm-up of the engine and for heating the catalyst. The demands on the metering accuracy are further increased by the increasing injection pressures of modern injection systems.

The present invention will be described below using the example of injectors in high-pressure injection systems. However, it is basically applicable to all injectors in which there is a relationship between a drive time (also referred to as drive time) of the injector and an amount of fuel injected by the injector. The invention is suitable and intended for use in both diesel and gasoline injection systems.

Injectors may be coupled to a drive signal, e.g. a drive current or a drive voltage to be controlled. For this purpose, an injection request - e.g. in the form of an injection quantity, an injector drive duration or a variable derived therefrom or applied thereto. The relationship between the driving duration and the injected fuel quantity can be indicated by an injection characteristic. Although the injected fuel quantity increases with increasing activation duration, the characteristic curve does not run linearly in all areas, and in some cases does not increase monotonically.

Conventional injectors have injector elements (in particular a so-called needle), which do not open completely for very short activation periods (so-called partial stroke). Although the characteristic curve does not run linearly in the partial stroke range, it increases monotonously. If the injector element has reached the position of maximum opening (so-called full stroke), a further increase in the activation duration after a certain time, which results from different influences, leads to a more or less linear increase in the injection quantity.

In a transitional region between partial and full-stroke range, the characteristic usually does not run linearly or monotonically increasing. In addition, a clear specimen spread, e.g. due to manufacturing tolerances.

In order to control corresponding injectors, characteristic features of the injector in the form of application parameters are usually used in a precontrol. Here, for example, the mentioned injection curve is used. This is possible for the control in Vollhubbereich and partly in the Teilhubbereich without much difficulty. In the transition area, however, losses in the metering accuracy can be expected.

The DE 10 2009 003 214 A1 Addresses this problem and proposes a method in which the transition region for each injector is determined individually and hidden or skipped during operation of the internal combustion engine. The determination of the boundaries of the transition region required for this purpose can be based, for example, on the basis of one of DE 10 2004 015 745 known method by means of sensors. In practice, however, this is expensive.

There is therefore a need for simple and reliable ways to operate injectors.

Disclosure of the invention

According to the invention, a method for operating an injector and a computing unit for carrying it out with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

Advantages of the invention

Injection is usually done by issuing an injection request. Several partial injections of the same or different injection quantity can be requested in one injection train, ie for the same working cycle, for example so-called pre-injections and main injections in diesel injection processes or multiple partial injections in the case of Otto injection processes. As mentioned, a "request" may be, for example, an injection quantity, an activation duration of an injector or a derivative thereof or thereupon acting size (eg an amount of injection or fuel charged with an additional value). The present invention provides to establish at least one prohibited injection request area. This corresponds in particular to a region in which a corresponding injection characteristic does not run linearly and / or does not increase monotonically. It is understood, however, that other prohibited injection request ranges may be established. In particular, these are those areas in which an injection can not be performed safely, reproducibly and / or reliably.

Such prohibited injection request ranges are avoided in the present invention by increasing or decreasing the respective target injection request should the target injection request fall within such a prohibited injection request range. As a result, an (adjusted) operating injection request to be used for injection is defined on the basis of the desired injection request. The injector is then activated in accordance with the operating injection request, that is, for example, using a drive duration derived from a corresponding operating injection quantity. This is done e.g. by means of the injection curve with corresponding drive times.

The reduction or increase in the desired injection request can advantageously be compensated for by adapting the desired or operating injection request to at least one other injection. If, for example, a plurality of partial injections are used in a corresponding injection cycle or train, a reduction of a desired injection request of a first partial injection can be compensated by increasing an injection request of another, second partial injection or vice versa.

In this case, it should preferably be ensured that a second partial injection adapted in accordance with the compensation for its part does not fall into the prohibited injection request range after the adaptation. In certain cases, however, this can also be tolerated or provided that the second partial injection falls within the prohibition range. For example, depending on an emission relevance, an operating injection request in the prohibited area can be tolerated. For compensation, in particular, the partial injections with the largest injection volumes of the injection train offer, because here usually a full stroke is present over a longer period. Compensation of a smaller partial injection is thus possible for sure.

In addition to a compensation between partial injections in the same cylinder and cycle, a cross-cylinder and / or cross-cycle compensation can be made, so that the total injection quantity remains constant, although the target injection request has been adjusted if necessary.

The at least one prohibited injection request area can be determined, for example, by individually measuring the particular injector used and / or a series of similar injectors. For example, it is possible to define at least one prohibited injection request range for a specific series. In this case, safety buffers can be used so that it is reliably avoided that the injector is controlled in corresponding characteristic ranges. An injector - individual measurement, as for example for previously mentioned methods of DE 10 2009 003 214 A1 is required, not applicable. The invention avoids the detour via the determination of the time of flight, from which then a drive function is to be determined, which in turn serves to determine drive durations for setpoint injection requests. On the other hand, according to the invention, much less expensive certain injection requirements are "forbidden" and the setpoint injection requirements are adjusted. The compensation is done as explained.

A corresponding prohibited injection request area is advantageously determined as a function of an injection pressure and / or a fuel temperature and can thus be adapted to the respective operating conditions.

An arithmetic unit, e.g. a control device, is, in particular programmatically, adapted to perform a method according to the invention. The implementation of the method in the form of software is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and therefore exists anyway. Suitable data carriers for providing the computer program are in particular hard disks, flash memories, EEPROMs, CD-ROMs and DVDs. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

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

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawings

1 shows a highly schematic representation of an internal combustion engine with a fuel injection system and a plurality of injectors.

2 illustrates a method according to an embodiment of the invention based on a characteristic.

3 shows a method according to an embodiment of the invention in the form of a flowchart.

Embodiment (s) of the invention

In 1 is an internal combustion engine 10 shown a fuel tank 12 comprising, by means of a conveyor system 14 Fuel in a high-pressure fuel line 16 is encouraged. The high pressure line 16 is designed for example as a common rail. The high pressure line 16 is with injectors 18 connected, which allow fuel directly in the injectors 18 each associated combustion chambers 20 inject. The operation of the internal combustion engine 10 and in particular the fuel injection system, for example, by the conveyor system 14 , the high pressure line 16 and the injectors 18 is formed by a computing unit, here a control unit 19 , controlled or regulated. The control unit 19 enables the acquisition of input values and the provision of output values or the actuation of actuators, in particular the control of the injectors 18 ,

The control unit 19 is program-technically designed to carry out a method according to the invention. For this purpose, for example, a memory device is used in the control unit, in which one or more prohibited injection request areas are stored. These can be stored, for example, before the delivery of the internal combustion engine. Alternatively or additionally, the data may be renewed during scheduled maintenance work, such as workshop visits, customer services, etc.

Injection may occur upon an injection request by the controller 19 energized an injector for a certain drive duration, so that the injector opens and fuel can escape.

Although in 1 a diesel engine is described, it should be emphasized that the driving method described above and explained below is independent of the type and, for example, can also be used in gasoline engines.

With reference to the 2 and 3 Now, a preferred embodiment of a method according to the invention will be explained.

Fuel is released when opening the injector at a pressure close to that in the high pressure line 16 corresponds, injected into the combustion chamber. The injected fuel quantity is proportional to the switch-on or drive time of the injector at a given pressure and long actuation periods 18 ,

For short drive durations, i. if only a partial stroke of a Injektornadel takes place, the relationship between the driving time and injected fuel quantity is not linear, a corresponding characteristic curve, however, usually increases monotonically. After reaching the full stroke, the relationship between the additionally injected amount of fuel and the driving time is linear. In the transition region between partial and full strokes, in which the injector needle just reaches its mechanical or hydraulic stop and is decelerated accordingly, the characteristic usually does not extend linearly or monotonously.

2 shows a characteristic 2 that one through an injector 18 indicates injected fuel quantity rk on the ordinate over a drive time ti on the abscissa. The characteristic has three sections 21 . 22 and 23 on. A first section 21 the characteristic 2 corresponds to the illustrated partial lift of the injector 18 , a second section 22 the transitional area between partial and full lift and a section 23 the full stroke. In the first part 21 has the characteristic 2 Although not a linear, but a monotonically increasing course. In the second section 22 the characteristic is neither linear nor monotonically increasing. In the third section 23 the characteristic curve is linear again and increases.

The boundaries between the sections 21 and 22 such as 22 and 23 can be made using a method as outlined in the DE 10 2004 015 745 A1 is known to be determined injector individually by means of a Nadelhuberfassung the Injektornadel. The DE 10 2009 003 214 A1 suggests, as explained before, perform an injector-individual detection of the needle lift and the section 22 "Hide".

For this purpose, a so-called time of flight of an injector member, eg the injector needle, is correlated with the activation duration. The time of flight is the time when the injector member is not in the closed position, ie is lifted off its seat. Also the characteristic of the flight time depending on the driving time has the said sections. The border between the sections 21 and 22 here forms a local maximum, the boundary between the sections 22 and 23 a local minimum. If the local maximum has at least the same value as the local minimum, any desired time of flight of the second section can 22 , that is, the transition area, can also be realized with a driving time outside the section 22 lies.

The procedure, like the DE 10 2004 015 745 A1 Therefore, it is imperative to include a method by which the boundaries of the transitional area can be identified on the basis of a measurement of the time of flight. This is expensive in practice. In addition, in such a method, modified characteristics need to be established that provide a relationship between appropriately modified drive durations of an injector 1 and the resulting injected fuel amounts, and then, instead of an original characteristic, as in 2 is shown, can be used.

The method proposed in the context of the invention, however, starts directly from a desired injection request (eg a desired injection quantity) rk, which is specified as usual. This is determined on the basis of a relationship known for a corresponding injector between actuation duration ti and injected fuel quantity rk, for example by means of the characteristic curve 2 , implemented in a drive time ti. However, certain injection requirements are "forbidden" from the outset.

A corresponding prohibited injection request area may, for example, here comprise the area between the points rkmin and rkmax. In this case, rkmax denotes the maximum quantity of the fuel which can be injected in the partial stroke, rkmin the minimum quantity of the fuel which can be injected in the full stroke. Of the fuel quantities rkmax and rkmin, e.g. From an injector measurement known that they are still injected in the partial stroke or even in full stroke. Here, appropriate security buffers can be specified. A prohibited injection request area, e.g. the limits rkmax and rkmin, is advantageously determined as a function of an injection pressure and / or a fuel temperature.

The determination of the prohibited injection request range thus avoids the activation of the injector with a drive duration that is in the range 22 the characteristic 2 would fall. The injection becomes more precise as a result.

When considering the characteristic 2 However, it can be stated that certain injection quantities, in this case the desired injection quantities rk2 and rk3, can only be achieved if an activation duration ti2 or ti3 was used, which is in the section 22 thence. However, this would lead to unsatisfactory results for the reasons explained above. If such a desired injection quantity rk2 or rk3 is requested, this is as shown by the arrows 24 and 25 reduces to an operating injection quantity rk2 'and rk3', respectively. The operation injection amounts rk2 'and rk3' may be the same or different. For example, it is always possible to use an operating injection quantity rk2 'or rk3' which corresponds to the explained value rkmax. However, it is also possible to apply a set injection quantity rk2 or rk3 to a fixed or variable offset or a function which shifts them out of the prohibited area.

Since the target injection quantities rk2 and rk3 were reduced in the present example (an increase, for example, to the value rkmin would also be possible), the total injected fuel amount would change without otherwise compensating. According to a preferred embodiment of the invention is now intended to maintain the total injection quantity. This can be done by increasing the injection quantity of another partial injection (here rk1).

The desired injection quantities rk2 and rk3 are, for example, nominal injection quantities for pilot injections (or, more generally, injections of lower volumes). The compensation may be effected by adjusting a desired injection quantity rk1 for another injection, for example the main injection (or, more generally, the higher volume injection) in the direction of a value rk1 '. This is by arrow 26 illustrated. The adjustment is made by the value by which the target injection quantities rk2 and rk3 have been reduced overall.

For the respective requirements (here fuel quantities or masses) this results in: rk2: Reduction on rk2 ' rk3: Reduction to rk3 ' rk1: Increase to rk1 ', where rk1 '= rk1 + rk2 - rk2' + rk3 - rk3 '

Scope and target values of corresponding compensations are in no way limited. For example, this may include the following adjustments, not shown: rk1: Reduction on rk1 ' rk3: Reduction to rk3 ' rk2: Increase to rk2 ', where rk2 '= rk2 + rk1 - rk1' + rk3 - rk3 '

It is understood that the method has been described here only by way of example and is also functional with a different number of injections and / or with several prohibited areas.

The decision in which direction a desired injection quantity or request, eg rk2 or rk3, is shifted, ie whether a reduction or increase takes place, can also be made dependent on which compensation can be made in another injection. For example, if rk1 were close to rkmin, a reduction required for compensation would be rk1 'in the range 22 the characteristic 2 move. This would also be within the scope of the invention, but may not be desirable, so that compensation should be made here rather by an increase in the amount of rk1. It may also be advantageous to balance an increase in rk2 by a decrease in rk3, and vice versa, without changing rk1.

In this context, of course, the requirements of the combustion process and environmental conditions can be taken into account.

In 3 a method according to a particularly preferred embodiment of the invention is shown in the form of a schematic flow chart and in total with 3 designated. The procedure 3 runs, as by the arrow 310 illustrates, for. B. cyclically according to the respectively provided injection cycles or successive injections. The method is here only for an injector 18 However, in principle, it can be used for any number of injectors 18 Find application, either a sum control (even groups) or an individual control can be made. The procedure 3 For example, in the controller 19 or a corresponding arithmetic unit, also programmatically implemented.

In one process step 31 becomes, as with impact arrow 311 illustrates a desired injection request predetermined. At least one prohibited injection request area may also be predetermined or stored permanently in a corresponding facility. Also appropriate injection, environmental or operating conditions can find input.

In a next process step 32 an evaluation of the in step 31 predetermined desired injection request in response to the at least one prohibited injection request area. If necessary, this is how with effect arrow 321 illustrates a compensation value derived from a different injection and possibly buffered as further explained below. step 32 can also consider other conditions.

In a further process step 33 is decided as based on the evaluation in process step 32 is to proceed. For example, as indicated by N, if the target injection request does not fall within the prohibited injection request range, it is set as the operation injection request and the injection control is set 1 can take a next step 34 done directly with the target injection request.

If this is not the case, that is, if it is determined that the desired injection request falls within the prohibited injection request range, it is determined in one step 35 increases or decreases the target injection request to determine the operating injection request until it no longer falls within a prohibited injection request range. The operation injection request then becomes in step 34 instead of the desired injection request of the control of the injector 1 based on. According to the preferred embodiment shown here takes place in this case also, as by impact arrow 321 illustrates a compensation of another, eg the next injection. A corresponding value, including several injections, can be buffered and in one step 32 will be charged.

The process returns to the injection process 34 along 310 back to the beginning.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009003214 A1 [0009, 0017, 0034]
• DE 102004015745 [0009]
• DE 102004015745 A1 [0034, 0036]

Claims (12)

Procedure ( 3 ) for operating at least one injector ( 18 ) of an internal combustion engine with the following steps: a) setting at least one prohibited injection request area ( 32 b) predetermining a desired injection request (rk1, rk2, rk3), c) if the desired injection request (rk2, rk3) into the at least one prohibited injection request range ( 32 ), determining an operating injection request (rk2 ', rk3') that does not fall into the at least one injection quantity prohibiting range ( 32 ) by decreasing or increasing the desired injection request (rk2, rk3), d) driving the at least one injector ( 18 ) according to the operation injection request (rk1, rk2 ', rk3'). Procedure ( 3 ) according to claim 1, wherein a plurality of injections are made and a desired injection request (rk2, rk3) is set for each of the plurality of injections, wherein, for at least one of the plurality of injections, an operational injection request (rk2 ', rk3') is made by reducing or increasing the For at least one further injection of the plurality of injections, the target injection request (rk1, rk2, rk3) is adjusted to compensate for the decrease or increase. Procedure ( 3 ) according to claim 2, wherein the plurality of injections comprise a plurality of partial injections of an injection train. The method of claim 2 or 3, wherein the operational injection request (rk2 ', rk3') for the at least one of the plurality of injections is determined such that the target compensation injection request (rk1, rk2, rk3) adapted to compensate for the decrease or increase is the at least one further injection of the multiple injections after the adaptation is not included in the at least one injection quantity prohibition range (FIG. 32 ) falls. Method according to one of the preceding claims, wherein the one injection request represents an injection quantity, injector drive duration and / or values derived therefrom. Procedure ( 3 ) according to one of the preceding claims, in which the at least one injector ( 18 ) based on an injection characteristic ( 3 ), which has a relationship between activation duration (ti) and injection quantity (rk) of the at least one injector ( 18 ), wherein the at least one forbidden injection request area ( 32 ) corresponds to an area in which the injection characteristic ( 3 ) is nonlinear and / or not monotonic. Procedure ( 3 ) according to one of the preceding claims, in which the at least one forbidden injection request area ( 32 ) a transition between a partial lift and a full lift of an injector element ( 111 ) of the at least one injector ( 18 ) corresponds. Procedure ( 3 ) according to one of the preceding claims, wherein the at least one prohibited injection request area is set in dependence on an injection pressure and / or a fuel temperature. Method according to one of the preceding claims, in which the at least one prohibited injection request area ( 32 ) by individually measuring the at least one injector ( 18 ) and / or a series of similar injectors ( 18 ) is determined. Arithmetic unit ( 19 ), in particular motor vehicle control device, which is adapted to carry out a method according to one of the preceding claims. Computer program with program code means which cause a computer or a corresponding computing unit to carry out a method according to one of claims 1 to 9 when executed on the computer or the corresponding arithmetic unit. A machine-readable storage medium having a computer program stored thereon and having program code means for causing a computer or corresponding computation unit to perform a method according to any one of claims 1 to 9 when executed on the computer or the corresponding computation unit.

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