EP1386075B1 - Method of operating a direct fuel injected internal combustion engine - Google Patents

Description

The present invention relates to a method for Operating a direct injection gasoline engine in particular a motor vehicle. at The process is gasoline in a combustion chamber of the Internal combustion engine injected directly and a spark in ignited the combustion chamber.

The invention also relates to a storage element for a Control unit of a direct-injection gasoline internal combustion engine in particular a motor vehicle. On the memory element is a computer program stored, that on a computing device, especially on one Microprocessor, is executable. The memory element is for example as a read-only memory, a random access memory or formed as a flash memory.

The present invention further relates to Computer program running on a computing device, in particular on a microprocessor, is executable.

Finally, the invention relates to a control device for a direct injection gasoline engine in particular of a motor vehicle. The control unit is used for control the injection of gas into a combustion chamber of the Brennkraftmaschine.und the ignition of a spark in the Combustion chamber.

State of the art

In known from the prior art Direct injection gasoline engines become gasoline directly into the combustion chamber of a cylinder Internal combustion engine injected. That in the combustion chamber compressed gasoline-air mixture is subsequently passed through Igniting a spark ignited in the combustion chamber. The Volume of ignited gasoline-air mixture expands explosive and displaces one in the cylinder. and movable piston in motion. The back and forth Movement of the piston is on a crankshaft Internal combustion engine transmitted.

Direct injection internal combustion engines can be used in operated different modes. As one first mode is a so-called. Shift mode known, the especially for smaller loads. As one second mode is a so-called. Homogenous operation known, the for larger, applied to the internal combustion engine loads is used. The different operating modes differ in particular in the injection time and the duration of injection as well as in the ignition time.

In shift operation, the gasoline during the Compression phase of the internal combustion engine in the combustion chamber so injected that at the time of ignition a cloud of fuel in the immediate vicinity of a Spark plug is located. This injection can be on done in different ways. So it is possible that the injected fuel cloud already during or immediately after injection at a spark plug is located and ignited by this. It is the same possible that the injected fuel cloud by a Charge movement led to the spark plug and then only is ignited. There is none for both combustion processes uniform fuel distribution in the combustion chamber, but a layer charge.

The advantage of the shift operation is that with a very small amount of fuel the adjacent smaller ones Loads from the internal combustion engine can be executed. However, larger loads can not by the Shift operation can be met.

In which provided for such large loads Homogenous operation is the gasoline during the intake phase of the Internal combustion engine injected, causing a turbulence and thus a distribution of gasoline in the combustion chamber yet before the ignition can be done without further notice. in this respect Homogenous operation corresponds approximately to the operation of Internal combustion engines, in which conventional manner Fuel is injected into the intake manifold. If necessary can even with smaller loads of homogeneous operation be used.

In stratified operation, a throttle in a to the Combustion chamber leading intake manifold wide open and the Burning is essentially only through the Controlled fuel mass and / or controlled regulated. In homogeneous operation, the throttle valve is in Depending on the requested moment closed and the fuel mass to be injected is in Dependent on the intake air mass controlled and / or regulated.

In both modes, ie in shift operation and in the Homogenous operation, the fuel mass to be injected additionally depending on a plurality of others Operating sizes on a with regard to Fuel saving, exhaust reduction, noise reduction and the like optimal value controlled and / or regulated. The control and / or regulation is in the two Operating modes different.

In spray-guided BDE combustion processes in stratified operation it makes sense, just before an injection nozzle, so at the ray root, to ignite. This can be sure be achieved that the spark gap of a spark plug in the Area of the jet root is located and the spark burns at a time when the geometric Radiant of the injected gas jet the Spark gap happened. As with the spray-guided BDE combustion process injected very late, the piston itself that is already near top dead center, is the Density of the gasoline-air mixture in the combustion chamber very high. That has a high Ignition voltage requirement, typically about 25 kV at one Electrode distance of 1 mm, the result. electrode spacings of significantly more than 1 mm are with a today for Not available ignition voltage of about 30 kV realizable.

However, it exists in particular with the spray-guided BDE combustion process the desire to electrode distances of significantly more than 1 mm, z. B. of 5 mm or more, to realize can, for. B. a plurality of individual beams of a Multi-hole nozzle together or once across the Ignite the jet root of the injection steel. so large electrode distances would ignite the gasoline-air mixture However, ignition voltages of significantly more than 50 kV, which, for reasons of size, the required isolation effort and high costs are not feasible.

The present invention is therefore the task underlying the safe and reliable inflammation of a Gasoline-air mixture in a combustion chamber of a direct injection internal combustion engine at a relative low ignition voltage with a spark plug with a allow significantly increased electrode spacing.

To solve this problem, the invention proposes starting of the method of operating a direct injection Gasoline internal combustion engine of the type mentioned above, that the spark ignited before the start of the injection and a spark duration until beyond the end of the injection stops out.

Advantages of the invention

According to the invention, the spark becomes such an early one Time ignited that the voltage applied to the spark plug Ignition voltage despite a large electrode gap because of the then still relatively low density in the Combustion chamber is sufficient. At the time of ignition of the Zündfunkens the piston is still relatively far from removed his top dead center and in the combustion chamber contained volume is not very strong yet compressed. The spark will then be up over the end of the after that injection. Because the Firing voltage of a spark plug significantly lower than that Ignition voltage is sufficient, the voltage applied to the spark plug conventional voltage of about 30 kV despite the significant increased spark gap to the spark strengthen and then burn with increasing density to let.

According to the invention it has been recognized that, in particular a spray-guided combustion process in the shift operation of for a successful ignition of the gasoline-air mixture required "physical" time range close to the end the injection is coupled since the mixture only can burn through successfully when the radiant is lit. This means that it only matters is, this "physical" time range of the burning time to cover the spark. It is irrelevant, if the spark is ignited much earlier or until burns much later. The thermodynamically relevant temporal position of the center of gravity of the combustion is so depending in particular on the beginning and the duration of the Injection.

The for the combustion of the gasoline-air mixture Required temperature will not be within the shortest time Time, due to a short-term spark applied. Rather, the required accumulates Ignition energy over a longer period of time, namely from the ignition of the spark before the beginning of the Injection until reaching the "physical" Time range following the end of the injection.

According to an advantageous embodiment of the invention is suggested that the internal combustion engine in one Shift mode is operated. Furthermore, will suggested that the internal combustion engine beamed is operated. Additional information about that spray-guided BDE combustion process can the "Automotive Handbook / Bosch" 22nd ed., Springer-Verlag, 1998, p. 369. To this Publication is expressly referred to.

According to another advantageous embodiment of The present invention proposes that the Spark duration lasts until the geometric end of a Injection jet has passed the ignition point. According to this Further education takes into account the fact that the Gasoline-air mixture can only blow through successfully, when the radiant end is lit. When the radiant one the ignition point has happened can, for example. By means of a in the combustion chamber projecting ion current probe can be determined. For more information on the ion current measurement method the "Kraftfahrisches Taschenbuch / Bosch", op. cit., p. 442 be removed. On this publication will be expressly referred to.

Of particular importance is the realization of the inventive method in the form of a Memory element used for a control unit direct injection gasoline engine in particular a motor vehicle is provided. It is on the Memory element stored on a computer program a computing device, especially on a microprocessor, executable and for the execution of the invention Method is suitable. In this case, so will the Invention by a stored on the memory element Computer program realized, so this with the Computer program provided memory element in the same Way the invention represents as the method, to whose Execution the computer program is suitable. When Memory element may in particular an electrical Storage medium are used, for example, a read-only memory, a random access memory or a flash memory.

The invention also relates to a computer program of of the type mentioned in the introduction method according to the invention is suitable when it is on the Calculator expires. It is particularly preferred if the computer program on a storage element, especially on a flash memory, is stored.

As a further solution to the problem of the present Invention is based on the control unit for a direct injection gasoline engine of the beginning mentioned type proposed that the control unit a Ignition of the spark before the start of the injection and a radio duration beyond the end of the injection causes.

Finally, as yet another solution is the task the present invention, starting from the direct injection gasoline engine of the beginning mentioned type proposed that the ignition system Ignition spark ignites before the start of the injection and a Spark duration beyond the end of the injection supplies.

drawings

Figur 1

eine erfindungsgemäße direkteinspritzende BenzinBrennkraftmaschine gemäß einer bevorzugten Ausführungsform;

Figur 2

ein Ablaufdiagramm eines erfindungsgemäßen Verfahrens gemäß einer bevorzugten Ausführungsform;

Figur 3

einen zeitlichen Ablauf des erfindungsgemäßen Verfahrens aus Figur 2 in Abhängigkeit von einer Drehwinkelstellung °KW einer Kurbelwelle der Brennkraftmaschine; und

Figur 4

eine Düse eines Einspritzventils der Brennkraftmaschine aus Figur 1 und einen von dem Einspritzventil eingespritzten Einspritzstrahl.

Other features, applications and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, which are illustrated in the drawing. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing. Show it:

FIG. 1

a direct injection gasoline engine according to a preferred embodiment of the invention;

FIG. 2

a flow diagram of a method according to the invention according to a preferred embodiment;

FIG. 3

a timing of the inventive method of Figure 2 in response to a rotational angle position ° KW a crankshaft of the internal combustion engine; and

FIG. 4

a nozzle of an injection valve of the internal combustion engine of Figure 1 and an injected from the injection valve injection jet.

Description of the embodiments

In Fig. 1 is a direct injection according to the invention Gasoline internal combustion engine 1 of a motor vehicle shown in which a piston 2 in a cylinder 3 hin- and is movable. The cylinder 3 is mit.einem combustion chamber 4 provided, inter alia, by the piston 2, a Inlet valve 5 and an exhaust valve 6 is limited. With the intake valve 5 is an intake pipe 7 and with the Exhaust valve coupled to an exhaust pipe 8.

In the area of the intake valve 5 and the exhaust valve 6 protrude an injection valve 9 and a spark plug 10 in the Brennraum 4. About the injection valve 9, gasoline in the Combustion chamber 4 are injected. With the spark plug 10 can ignites the gasoline-air mixture in the combustion chamber 4 become.

In the intake pipe 7 is a rotatable throttle valve 11th accommodated, via the intake pipe 7 air supplied is. The amount of air supplied depends on the Angular position of the throttle valve 11. In the exhaust pipe 8 is housed a catalyst 12, the cleaning of the by the combustion of the fuel-air mixture resulting exhaust gases used.

The piston 2 is due to the combustion of the fuel-air mixture 4 in a float, the is transmitted to a crankshaft, not shown, and on this a torque exerts.

A control unit 18 for controlling and / or regulating the direct injection internal combustion engine 1 is of Input signals 19 acted upon by means of sensors measured operating variables of the internal combustion engine 1 represent. For example. is the controller 18 with a Air mass sensor, a lambda sensor, a speed sensor and the like connected. Furthermore, the control unit 18 connected to an accelerator pedal sensor, which is a signal This creates the position of one of a driver operable accelerator pedal and thus the requested Indicates torque. The controller 18 generates Output signals 20, with which via actuators or Steller the Behavior of the internal combustion engine 1 can be influenced. For example. is the control unit 18 with the injection valve. 9 (Control signal EW), the spark plug 10 (control signal ZV), the Throttle valve 11 and the like connected and generates the necessary for their control signals.

Among other things, the controller 18 is provided to the Control operating variables of the internal combustion engine 1 and / or to regulate. For example. is the of the injection valve 9 in the Combustion chamber 4 injected fuel mass of the Control unit 18, in particular with regard to a small Fuel consumption, low pollutant development and / or a low level of noise control and / or regulated. For this purpose, the control unit 18 with a Microprocessor 21, which in a flash memory 22 has saved a computer program that is suitable is to perform said control and / or regulation and the invention explained in detail below Perform procedure.

The internal combustion engine 1 of FIG. 1 may be in a plurality operated different modes. That's the way it is possible, the internal combustion engine 1 in a homogeneous operation, a shift operation, a homogeneous lean operation or to operate like. In homogeneous operation, the fuel during the intake phase of the injection valve 9 directly in the combustion chamber 4 of the internal combustion engine 1 is injected. Of the Fuel is thus still largely until the ignition swirled, so that in the combustion chamber 4 a substantially homogeneous fuel-air mixture is formed. That too generating moment is essentially about the Position of the throttle valve 11 from the controller 18th set. In homogeneous operation, the operating variables the internal combustion engine 1 controlled and / or regulated that lambda = 1. The homogeneous operation is especially used at full load.

The homogeneous lean operation largely corresponds to the Homogenous operation, however, it will set the lambda to a value set greater than 1.

In shift operation, the fuel during the Compression phase of the injection valve 9 directly into the Combustion chamber 4 of the internal combustion engine 1 injected. In order to is not homogeneous when ignited by the spark plug 10 Mixture in the combustion chamber 4 available, but a Fuel stratification. The throttle valve 11 may, apart of requirements z. B. an exhaust gas recirculation and / or a tank vent completely open and the Internal combustion engine 1 to be operated entschrosselt. The moment to be generated becomes extensive during shift operation adjusted via the fuel mass. With the Shift operation, the internal combustion engine 1 in particular be operated at idle and at partial load.

Between the mentioned operating modes of the internal combustion engine 1 can be switched back and forth. such Switches are performed by the controller 18.

At the top of the piston 2 is a combustion bowl 23rd intended. The injection valve 9 is centric to the Burner trough 23 is arranged and has a 6- to 8-hole nozzle on. Through the combustion chamber 23 and the particular trained injection valve 9 may be a jet-guided Burning process can be realized. The internal combustion engine 1 is operated in shift mode. The gasoline-air mixture is immediately before the exit of the injection valve 9, so at the beam root, detonated. The spark plug 10 has On electrodes, between which after ignition of the Spark plug 10 forms a spark gap. Of the Electrode distance is a few millimeters, and is thus significantly above the usual electrode distance of about 1 mm. The relatively large electrode spacing has the Advantage that in an injection valve 9 with a Multi-hole nozzle many individual beams are ignited together or that across the jet root of a gasoline injection jet 51 (see Figure 4) can be ignited. In Fig. 4 is an injection nozzle 52 of the injection valve 9 and the injected into the combustion chamber 4 gasoline injection jet 51 is shown with its geometric beam end 50. The Spark gap is located in the area of the jet root. The spark plug 10 is so from the controller 18 controlled that a spark before the start of gasoline injection is ignited and the spark gap at least until the geometric end of radiation 50 (cf. 4) of the injection jet 51 passes the spark gap Has.

Since early, i. ignited at low density, is enough despite the relatively large electrode spacing a conventional ignition voltage of about 25 - 30 kV. The Ignition is in accordance with the present invention thereby reaches that spark generated by the spark plug 10 over a relatively long period of time in the combustion chamber 4 burning. This period begins before the beginning of the Injection and ends only after the end of the injection. For the production of the for the ignition of the gasoline-air mixture required temperature is therefore a relative long period available. By injecting the Gasoline in the combustion chamber 4 then becomes the combustion triggered.

In Fig. 3, the timing of the method of Fig. 2 is shown. With 40 of the injection curve, with the ignition timing 42 and 43 denotes an angular position ° CA of the crankshaft of the internal combustion engine 1. The spark duration of the spark is 44 and the duration of injection 45. In a _{spray-guided combustion process in stratified operation} , a so-called "physical" time range t _phy , which is closely coupled to the end 41 of the injection 45, is decisive for a successful ignition of the gasoline-air mixture. The gasoline-air mixture can burn through successfully only when the geometric beam end 50 (see Fig. 4) is ignited. This means that in particular the "physical" time range t _phy must be covered by the burning time 44 of the spark gap, which is also the case in the method _according to the invention. A relatively small influence on the combustion of the gasoline-air mixture has the beginning and end of the burning time 44, ie whether the spark is ignited much earlier than the physical time range t _phy or the spark gap burns until much later. However, the relatively long burning time 44 has an advantageous effect on the ignition voltage for the spark plug 10. Instead of a relatively high ignition voltage of, for example, 50 kV or more, which rests only briefly on the spark plug 10, a much lower voltage of, for example, 25 to 30 kV is sufficient to ignite the spark. The lower burning voltage of typically <2 KV but is for a longer period at the spark plug 10th

Ignition systems are particular to the present invention advantageous in which the burning time 44 of the spark or the spark gap is controllable. Such ignition systems are, for example, Pulszugzündungen, Pulszugzündungen with Energy transfer in the charging phase, AC ignitions or RF ignitions.

In Fig. 2 is a flow chart of an inventive Process illustrated. The procedure starts in one Function block 30. In a function block 31 is a Spark ignited from the spark plug 10 and burning held. In a function block 32 is gasoline in the Combustion chamber 4 of the internal combustion engine 1 injected. Of the Function block 32 includes all gasoline injection, from start to finish. After the end of the injection 45 In a functional block 33, the burning time 44 of FIG Spark gap ended. Preferably, it is waited until a geometrical end 50 of the injection jet 51 (cf. Fig. 4) has passed the ignition. In one Function block 34 then becomes the inventive method completed.

Claims (9)

1. Method for operating a direct-injection petrol internal combustion engine (1), in particular of a motor vehicle, in which petrol is injected directly into a combustion chamber (4) of the internal combustion engine (1) and an ignition spark is ignited in the combustion chamber (4), characterized in that the ignition spark is ignited before the injection (45) begins, and the spark duration (44) lasts beyond the end of the injection (45).
2. Method according to Claim 1, characterized in that the internal combustion engine (1) is operated in a stratified mode.
3. Method according to Claim 1 or 2, characterized in that the internal combustion engine (1) is operated in jet-controlled mode.
4. Method according to one of Claims 1 to 3, characterized in that the spark duration (44) lasts until the geometric end (50) of an injection jet (51) has passed the ignition location.
5. Memory element (22), in particular read only memory, random access memory or flash memory, for a control unit (18) of a direct-injection petrol internal combustion engine (1), in particular of a motor vehicle, on which a computer program is stored, which can run on a computer unit, in particular on a microprocessor (21), and is suitable for carrying out a method according to one of Claims 1 to 4.
6. Computer program which can run on a computer unit, in particular on a microprocessor (21), characterized in that the computer program is suitable for carrying out a method according to one of Claims 1 to 4 when it runs on the computer unit.
7. Computer program according to Claim 6, characterized in that the computer program is stored on a memory element (22), in particular on a flash memory.
8. Control unit (18) for a direct-injection petrol internal combustion engine (1), in particular of a motor vehicle, for controlling and/or regulating the injection of petrol into a combustion chamber (4) of the internal combustion engine (1) and igniting an ignition spark in the combustion chamber (4), characterized in that the control unit (18) causes the ignition spark to be ignited before the injection (45) begins and causes the spark duration (44) to last beyond the end of the injection (45).
9. Direct-injection petrol internal combustion engine (1), in particular of a motor vehicle, the internal combustion engine (1) having a fuel injection system for the direct injection of petrol into a combustion chamber (4) of the internal combustion engine (1) and an ignition system for igniting an ignition spark in the combustion chamber (4), characterized in that the ignition system ignites the ignition spark before the injection (45) begins and provides a spark duration which lasts beyond the end of the injection (45).

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