DE102006033932A1 - Internal-combustion engine i.e. diesel internal-combustion engine, operating method, involves performing injections such that minimum distance between consecutive injections depends on active fuel pressure influencing closing of valve unit - Google Patents

Abstract

The method involves performing fuel injections into an internal-combustion engine (10) i.e. diesel internal-combustion engine, using a fuel-injection device (16) such that a minimum distance between two consecutive injections of the fuel depends on an active operating parameter i.e. active fuel pressure, which influences the closing of a valve unit (18) of the fuel-injection device. The minimum distance depends on the active fuel pressure preferably in a fuel distributor. An independent claim is also included for a computer program for a method of operating an internal-combustion engine.

Description

State of the art

The The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1. The invention is further a computer program, an electrical storage medium, as well as a Control and / or regulating device according to the preambles of the siblings Claims.

In order to comply with current and future emission standards, multiple injection strategies are used in many internal combustion engines, especially in diesel internal combustion engines. In these, the fuel is introduced into the combustion chamber of the internal combustion engine within a working cycle with several injections, some of which are close to one another. As a result, the total injection is divided into pre-, main and post injections. Such an injection strategy is also called "split injection". From the DE 100 64 505 A1 a method is known with which a distance between a first injection process and a second injection process can be monitored within a working cycle of a cylinder of an internal combustion engine.

Disclosure of the invention

Technical task

task The present invention is a method of the aforementioned To provide a way to control emissions and noise Operation of an internal combustion engine can be reduced.

Technical solution

These The object is achieved by a method having the features of the claim 1 solved. Advantageous developments are specified in subclaims. Other solutions are in the independent claims called. About that In addition, essential features of the invention can be found in the following Description and the drawing, the features also in whole different combinations for the invention essential could be, without being explicitly pointed out.

Advantageous effects

According to the invention was recognized that it can happen in the previous procedures that two successive injections so close together, that they "fuse" into a single injection. This means that the total injection quantity is higher as the desired target amount, which at best has a negative impact the emissions, the noise and the operating behavior of the internal combustion engine has, in the worst Case, however, to damage lead the internal combustion engine can. As a reason for Such fusion of two injections has been recognized even if the drive signals of the two injections a Distance from each other, this due to the inertia of the valve member for the Lifting motion does not necessarily apply. It is therefore possible that the valve element not yet on his before the control of the subsequent injection Seat returned is.

According to the invention will now a minimum distance between two successive injections defined by at least one current, the closing of the Valve element influencing operating size of the internal combustion engine depends, or in other words, the minimum distance is defined to ensure that is that the valve element is closed or returned to its seat is before it for a subsequent injection again moved away from its valve seat becomes. In contrast to the definition of a rigid minimum distance is by dependence the minimum distance of the said operating size of the internal combustion engine ensures that this minimum distance is always as short as possible, so that tight successive injections are still possible.

hereby is achieved that for cheap emissions required multiple injection strategies can be used, thereby however, the distances be kept very short between the individual injections can, without the risk of a merger of successive Injections exists. Also, a deterioration of the operating noise of Internal combustion engine is avoided, and certainly damage due to too big Fuel injection quantities kept away from the internal combustion engine.

at a particularly advantageous embodiment of the method according to the invention depends on the minimum distance from a current fuel pressure, preferably in a fuel rail, from. It has been found that the fuel pressure is the closing of the Valve element in a special way influencing operating variable. It can be assumed that the valve element is faster closes the bigger the Fuel pressure is. At higher Fuel pressure, therefore, the minimum distance will be rather small.

The minimum distance may also depend on a previous drive duration of the fuel injection device. This is based on the consideration that the valve element all the more further away from its valve seat, the longer the actuation time is. However, a large distance of the valve element from its valve seat means an increased time that the valve element needs again for closing. In other words: the larger the preceding activation duration, the greater the minimum distance to the subsequent injection should be selected.

advantageously, fuel pressure and previous activation time are fed into a map, which outputs a value used to determine the minimum distance serves or is itself the minimum distance.

A further closing the operating element of the internal combustion engine influencing the valve element is the fuel temperature. This affects the density of the fuel, which in turn affects its flow behavior and compressibility. Therefore the minimum distance may be additional also from a current fuel temperature.

Also the current temperature of the internal combustion engine can be used in the determination the minimum distance become. Such a temperature of the internal combustion engine is usually based on the temperature of a cooling fluid the internal combustion engine or a temperature of a cylinder head of the Internal combustion engine determined. The temperature of the internal combustion engine influenced by temperature-related expansions of the components in the fuel injector their fits, which also the time that the valve element for the closing process needed can influence.

Especially It is advantageous if the influence of the fuel temperature and / or the current temperature of the fuel injection device or the Internal combustion engine to the minimum distance by the formation of a Weighting factor considered with which an additive term is weighted, preferably depends on the fuel pressure and the previous drive duration. hereby will the precision increased in the determination of the minimum distance, since the influence of this two company sizes in one Operating point of the internal combustion engine may be greater than in another Operating point.

A further advantageous embodiment of the method according to the invention is characterized by the fact that another minimum distance between two consecutive injections of an electric Operating size of the internal combustion engine depends and that as a minimum distance the larger of the two determined minimum distances is used. For the activation of an actuator of the fuel injection device, for example, an electromagnetic or piezoelectric Actors, usually A capacitor that uses the required energy in the shortest possible time Can give time to the actor. However, such a capacitor must be be charged, which requires a certain amount of time. In these traps will be the "electric conditional "minimum distance that period of time required between two actuations is to charge such a capacitor. But also other electrical Company sizes can be used for education an "electric conditional "minimum distance between two consecutive injections are used.

By the selection of the maximum value of "electrical" minimum distance and "hydraulic" minimum distance (this is the minimum distance that one of the closing the valve element influencing operating variable of the internal combustion engine depends) is on the one hand to ensure that even close succession of injections On the other hand, it is ensured that these injections at all in the desired Way and with the desired stroke performed the valve element can be. Ultimately, therefore, this is also the emission and consumption behavior the internal combustion engine positively influenced.

drawing

Brief description of the drawings

following will be a particularly preferred embodiment of the present invention Invention explained in more detail with reference to the accompanying drawings. In show the drawing:

1 a schematic representation of an internal combustion engine with a plurality of fuel injection devices;

2 a diagram in which a control of one of the fuel injectors of 1 is plotted over time;

3 a representation similar 2 but for a stroke of a valve element of the fuel injection device; and

4 a block diagram of a method for determining a minimum distance between the two in the 2 and 3 shown successive injections.

Embodiments of the invention

An internal combustion engine carries in 1 Overall, the reference number 10 , It includes an engine block 12 with several combustion chambers 14 , force fabric gets into the combustion chambers 14 directly each by means of a fuel injection device 16 injected. For this purpose, each of the fuel injectors 16 via a needle-like valve element 18 , which with a housing-side valve seat (not shown) of the fuel injection device 16 works together and by an actor 20 is pressed. The fuel injectors 16 are to a fuel rail 22 connected, which is also called "Rail". The fuel is in the rail 22 stored under high pressure. For this purpose, the fuel via a high-pressure conveyor 24 in the rail 22 promoted.

The operation of the internal combustion engine 10 is controlled by a control device 26 controlled and regulated. To do this, it receives signals from various sensors, including a temperature sensor 28 , which is a temperature of a cooling water of the internal combustion engine 10 detected and by a pressure sensor 30 who's in the rail 22 prevailing fuel pressure detected. Furthermore, another temperature sensor 32 working in the high-pressure conveyor 24 detects the temperature of the fuel, the control and regulating device 26 appropriate signals ready. To be controlled by the control and regulating device 26 including the actors 20 the fuel injectors 16 ,

Depending on the duration of the activation of an actuator 20 remains the valve element 18 lifted from its housing-side valve seat shorter or longer, so that less or more fuel in the corresponding combustion chamber 14 arrives. This principle is not limited to any type of internal combustion engine, but may, as well as the method shown below, be applied to very different engine types, such as internal combustion engines with gasoline and those with direct diesel injection. Also, the following procedure is for different types of fuel injectors 16 applicable, for example, those in which the valve element 18 directly from the actuator 20 is actuated, as well as those in which the actuator 20 belongs to a hydraulic control valve, which in turn has a control pressure for the valve element 18 affected.

In order to operate the internal combustion engine 10 To produce as few emissions as possible, a multiple injection strategy is used, in which within a working cycle of the fuel through a plurality of individual injections from the fuel injection device 16 in the associated combustion chamber 14 is injected. In order to accommodate as many such individual injections within a working cycle, the distances between the individual injections should be as small as possible. On the other hand, it should be avoided in any case that the distance between two successive injections is so low that due to the inertia of the valve element 18 this has not yet returned safely to its housing-side valve seat when it should open again for the next injection.

The ratios of two closely spaced injections are from the 2 and 3 apparent: in 2 is a drive signal A, with which the control and regulating device 26 the actor 20 the fuel injector 16 controls, plotted over time t. One recognizes a first drive signal A1 for a first injection 34 and a second drive signal A2 for a second injection 36 , Between the end of the first drive signal A1 and the beginning of the second drive signal A2 is a time interval which is denoted by D1. In 2 are the corresponding strokes H1 and H2 of the valve element 18 applied over time t. It can be seen that after a short bouncing of the valve element 18 at its valve seat (reference numeral 38 in 3 ) the valve element 18 safely rests again on its housing-side valve seat (stroke = 0) before the second drive signal A2 begins and the valve element 18 those for the second injection 36 required stroke H2 begins. The distance D1 corresponds to a minimum time interval between the two successive injections 34 and 36 which must be adhered to so that it is the two injections 34 and 36 are really two discrete and separated, so not merged with each other injections. This minimum distance D1 depends on several, the closing of the valve element 18 (Area 40 the curve H1) influencing operating variables of the internal combustion engine 10 from. This will now be with reference to 4 explains:

The from the pressure sensor 30 recorded pressure PR in the rail 22 and a duration AD1 of the first injection drive A1 34 are fed into a map KF1, which outputs a first raw minimum distance D1. The pressure PR and the drive duration AD1 are also fed into a map KF2, which outputs a second minimum raw distance D11. This one will be in 40 multiplied by a factor F1, which is generated by a characteristic KL1, in which the temperature sensor 32 determined temperature TF of the fuel is fed. The multiplication in 40 gives an additional minimum distance DF11, weighted by the fuel temperature TF. In the case of an embodiment, not shown, which does not include a pressure sensor, the speed nmot could be fed into the maps KF1, KF2 and KF3, since the pressure is speed-dependent. The latter applies in particular to pump-nozzle and distributor injection systems.

The fuel pressure PR and the drive duration AD1 are also fed into a map KF3, which outputs a third raw minimum distance D12. This one will be in 42 multiplied by a second factor F2, which is generated by a characteristic KL2. In turn, a temperature TE is fed into this, which on the temperature sensor 28 detected cooling water temperature based. By the temperature TE should with the best possible accuracy, the temperature of the fuel injection device 16 be expressed. The transition from the temperature sensor 28 detected cooling water temperature to the temperature TE can be done for example by means of suitable models. By multiplying in 42 a second additional minimum distance DF12 is generated, which is determined by the temperature TE of the fuel injection device 16 weighted.

The two additional minimum distances DF11 and DF12 are in 44 adds and thus gives an additional minimum distance DF. This one will be back in 46 added to the first raw minimum distance D10, resulting in the actual, by the hydraulic closing behavior of the valve element 18 conditional minimum distance D1 (compare 3 ) leads. This is as well as a second minimum distance D2 in a block 48 fed, in which the greater of the two values D1 and D2 selected and ultimately output as a minimum distance D. The second minimum distance D2 is based on an electrical operating variable of the internal combustion engine 10 , For example, the time constant of a capacitor (not shown) of the control and regulating device 26 , which is used to control the actuator 20 the fuel injector 16 serves.

Like from the 2 and 3 can be seen, the minimum distance D2 in the present case considered significantly smaller than the minimum distance D1. Would the second control not start only after the minimum distance D1, but already after the minimum distance D2, which is in 2 indicated by a dot-dash line labeled 'A2', the valve element would 18 with the hub (in 3 also shown in phantom and designated HZ) begin, even before the stroke H1 of the previous injection 34 finished. By selecting the maximum value in 48 will ensure that the two injections 34 and 36 are actually separated from each other and do not merge.

Claims (12)

Method for operating an internal combustion engine ( 10 ), in which the fuel within a working cycle by means of a fuel injection device ( 16 ), the at least one valve element ( 18 ), by a plurality of injections ( 34 . 36 ) in a combustion chamber ( 14 ) of the internal combustion engine ( 10 ), characterized in that a minimum distance (D1) between two successive injections (D1) 34 . 36 ) of at least one current, the closing of the valve element ( 18 ) influencing operating variable (PR, AD1) of the internal combustion engine ( 10 ) depends. A method according to claim 1, characterized in that the minimum distance (D1) from a current fuel pressure (PR), preferably in a fuel rail ( 22 ) depends. Method according to one of claims 1 or 2, characterized the minimum distance (D1) from a preceding activation time (AD1) depends. Process according to claims 2 and 3, characterized that the fuel pressure (PR) and the previous driving time (AD1) in a map (KF1, KF2, KF3) are fed. Method according to one of the preceding claims, characterized characterized in that the minimum distance (D1) from a current Fuel temperature (TF) depends. Method according to one of the preceding claims, characterized in that the minimum distance (D1) from a current temperature (TE) of the internal combustion engine ( 10 ) or the fuel injection device ( 16 ) depends. Method according to one of claims 5 or 6, characterized in that the influence of the fuel temperature (TF) and / or the current temperature (TE) of the fuel injection device ( 16 ) or the internal combustion engine ( 10 ) to the minimum distance (DA1) by the formation of a weighting factor (F1, F2), with which an additive term (D11, D12) is weighted, which preferably depends on the fuel pressure (PR) and the preceding driving duration (AD1). Method according to one of the preceding claims, characterized in that a further minimum distance (D2) between two successive injections (D2) 34 . 36 ) of an electrical operating variable of the internal combustion engine ( 10 ) and that the greater of the two determined minimum distances (D1, D2) is used as the minimum distance (D). Method according to one of the preceding claims, characterized characterized in that the minimum distance from a speed of the internal combustion engine depends. Computer program, characterized in that it is for use in a method according to programmed one of the preceding claims. Electrical storage medium for a control and / or regulating device ( 26 ) an internal combustion engine ( 10 ), characterized in that on it a computer program for use in a method of claims 1 to 9 is stored. Control and / or regulating device ( 26 ) for an internal combustion engine ( 10 ), characterized in that it is programmed for use in a method according to one of claims 1 to 9.