EP1336040B1 - Method for injecting fuel during the starting phase of an internal combustion engine - Google Patents

Description

The present invention relates to a method of injection of fuel in a multi-cylinder internal combustion engine.

It is known at the start of a gasoline engine, the cylinder ever once with a so-called pre-injector, to wet the cylinder walls and at the same time an ignitable To provide mixture for the first combustion. There At this time, no synchronization between the camshaft and the crankshaft present and the position of Piston is unknown, is a targeted pre-injection strategy required to exhaust unburned fuel and thus minimize pollutant emissions during takeoff.

In a method known from EP 0 371 158 A1 the cylinders depending on the two different ones Levels of the camshaft signal in a first and a second Cylinder group divided. The cylinders of the first group be immediately after a starter ID at the same time the pilot injectors (group injector) supplied while the cylinders of the second group are delayed in time with the Pre-injectors are supplied, either in a predetermined Order or in normal sequential order, depending on whether a synchronization between camshaft and crankshaft has already taken place.

It has now been shown that in this process in 50% not all prebeaters for the cylinders of the launches first group come to the burning, since a part of the Vorabeinspritzer depending on the standstill position of Internal combustion engine and the position of the intake valves an open or just closing inlet valve hits. Such a condition should be stricter with regard to getting stricter will be avoided by the statutory exhaust regulations. A corresponding excessive emission of pollutants could be Although this avoided that the Vorabeinspritzer first discontinued when the exact position and assignment between Crankshaft and camshaft are known, so then one "sequential start" could be performed. The episode but would be a delayed start.

The present invention is based on the object Method of injecting fuel into a multi-cylinder Specify internal combustion engine, which is an emission-optimized Quick start of the engine allows.

The method according to the invention is defined in claim 1.

The present invention is based on the finding that a Internal combustion engine after switching off in disengaged Condition always at certain discrete positions remains, with the number of discrete positions over two Crankshaft revolutions (760 °) always the number of cylinders equivalent. Thus, in the case of n cylinders, these are n stop angle positions.

When the internal combustion engine starts, these are n stoppage angle positions initially unknown. With the help of the camshaft signal However, the number of unknown stall angle positions can be reduced to n / 2. Thus, can in the inventive method depending on the Camshaft signal and the stored stationary angle positions a cylinder to be selected first is supplied with a pre-injection, while the rest Pre-injection will be discontinued later. In contrast to the above-described prior art method thus become the first cylinders not at the same time, but always in time offset from each other supplied with the pre-injectors.

Preferably, in dependence on the camshaft signal, the one subdivision of each working game into two segments corresponding to two consecutive crankshaft revolutions allows the standstill angle positions in two groups subdivided, and it is determined that group, which the current stall angle position at which the Internal combustion engine has stopped. advantageously, Only the cylinder of the first group, its inlet valve with delivery of the first pilot injector with certainty closed or at least predominantly closed is the first to be provided with an advance injector.

To determine the order of the next pre-injectors, is expediently the angular distance between the Angular position at which the first pilot injector delivered is, and the angular position of the first synchronization pulse stored with the angular distance between two adjacent ones Standstill angle positions compared and in Dependence on this comparison the order of the next Pre-injector determined.

The inventive method ensures that all pre-injectors are actually involved in the incineration participate, so that the pollutant emissions, in particular the HC emissions to the level of a sequential start decline. Nevertheless, early fuel injection is possible so that the inventive method a faster Start compared to a sequential starting method allows.

Further advantageous embodiments of the invention are in defined in the subclaims.

Figur 1 eine schematische Schnittdarstellung einer Brennkraftmaschine in Form eines Ottomotors mit Benzineinspritzung;

Figuren 2 und 3 Diagramme, in denen über der Zeit Drehzahl-, Nockenwellen-, Kurbelwellen-, Einspritzventil- und Einlassventil-Signale aufgetragen sind.

The method according to the invention will be explained in more detail with reference to the drawings. It shows:

Figure 1 is a schematic sectional view of an internal combustion engine in the form of a gasoline engine with gasoline injection;

Figures 2 and 3 are graphs in which over time the speed, camshaft, crankshaft, injector and intake valve signals are plotted.

FIG. 1 shows a schematic partial section through a Internal combustion engine, which in the described embodiment for illustrative purposes as a four-cylinder gasoline engine is formed with gasoline injection.

The internal combustion engine 3 is a central one in the usual way electronic control unit 1 associated with the ignition, Fuel injection and other processes of the internal combustion engine controls. Each cylinder 7 is at least one inlet valve 6 and at least one injection valve 2 assigned. The Injector 2 injects fuel into the intake manifold immediately before or on the valve disk of the intake valve 6 from.

The crankshaft 8 is a crankshaft sensor 4 with a toothed Encoder wheel assigned to the crankshaft angle representative crankshaft signal CRK (see lower half of Figures 2 and 3) generated. The camshaft 5, which are the intake valves 6 controls and at half the speed of the crankshaft 8, a camshaft sensor 9 is for generating a camshaft signal CAM (see lower half of Figures 2 and 3) assigned. The camshaft 5 can be connected to the crankshaft 8 rotatably connected or angle adjustable relative to it be.

In Figures 2 and 3, lower half, are respectively the crankshaft signal CRK, the cam signal CAM and the speed N plotted over time. Each pulse of the crankshaft signal CRK corresponds to a tooth of the sender wheel, wherein a double tooth gap after every 60 teeth as a synchronization pulse S for each one full turn of the crankshaft 8 serves. The cam signal CAM has two different ones Level, the two consecutive revolutions associated with the crankshaft. The camshaft signal CAM and the crankshaft signal CRK with its synchronization pulses S allow an unambiguous assignment of the crankshaft position in the working game.

The camshaft signal may also have other pulse and level shapes exhibit; However, it should be ensured that the Camshaft signal a subdivision of each working cycle in two segments (ä 360 °) corresponding to two consecutive Crankshaft revolutions (720 °) allowed.

During normal operation of the internal combustion engine can therefore with Help the crankshaft signal and camshaft signal the Injectors 2 in the usual sequential injection mode be controlled and operated. At the start, however, is the Crankshaft position and thus the position of the piston still not known, and it is synonymous if synonymous nor sync between the camshaft and the crankshaft. An injection in the sequential injection operation is therefore not possible.

Experiments have now shown that an internal combustion engine after switching off in the disengaged state is always discrete Positions Stays. In a four-cylinder internal combustion engine these are exactly four positions over each 760 ° the crankshaft rotation. For the toothed sensor wheel of the crankshaft sensor 4 arise here, for example, always the positions either 20 (± 7) teeth or 50 (± 7) teeth before a synchronization pulse S. The angular distance between these positions is thus 180 ° (± 42 °). At a Six-cylinder internal combustion engine result in corresponding Way as positions for the toothed encoder wheel of the crankshaft sensor z. B. 5 or 25 or 45 teeth before the next Synchronization pulse S; the angular distance between the Positions is then 120 °. Generally, the number the standstill angle positions at which an internal combustion engine Stands, the number of cylinders corresponds. in the the rest has been shown that with increasing number of cylinders the standstill angle positions become more and more discrete.

The above-described facts in the inventive Exploited method, an optimal strategy for Dispensing of Vorabeinspritzern to develop during the starting phase. To explain this pre-injection strategy is Referring first to Figure 2 reference.

In the lower half of Figure 2 are in addition to the crankshaft signal CRK and the cam signal CAM, the speed N the internal combustion engine plotted over time. In the upper Half of Figure 2 are for the four cylinders 1 to 4 of Four-cylinder internal combustion engine, the drive signals IV1 - IV4 for the four injectors over time, where the four pre-injectors I with I1 - I4 are designated. In addition, the drive signals EV1 - EV4 are for the four Intake valves plotted against time, with the opening pulses for the opening of the inlet valves with E1 - E4 are. Also, in the top two lines 2 shows the pulses for the top dead center (TDC1 - TDC4) the four cylinders or top dead center (TDC1) of the cylinder 1 shown.

As indicated in Figure 2 in connection with the speed, is for the start of the engine, a starter E provided. At this time, the camshaft signal CAM either high or low, in the example of the figure 2 low level. Thus, e.g. as in the beginning Method according to EP 0 371 158 B1 - the cylinders 1 to 4 are divided into two groups (in the example of the Figure 2 in a first group with the cylinders 3, 4 and a second group with the cylinders 1, 2). In addition, this is also known if the internal combustion engine in the first both standstill angle positions or the second two Standstill positions has stopped. In other words, reduces the number of unknown stationary angle positions on two.

In the previously described prior art method at a predetermined angular distance to the starter identifier E (for example after eight recognized and valid teeth of the crankshaft sensor) the two cylinders 3, 4 of the first cylinder group supplied at the same time with the pilot injectors, such as is indicated by the pilot injectors I3 'and I4. in this connection However, the pre-injector I3 'would close just before closing associated intake valve EV3 are discharged, resulting in a Greasing of the fuel-air mixture and unburned emission Fuel would result.

According to the inventive method is therefore according to the Starter ID E only one cylinder, its inlet valve closed with security or mostly closed, supplied with the pilot injector .; in the example of Figure 2 this is the cylinder 4 with the pilot injector I4. The pre-injection I3 'is opposed, as by a dotted line P indicated, not delivered at this time.

As mentioned earlier, at the time of submission of the first Pre-injector I4 not yet known if the internal combustion engine at the first or second standstill angular position (eg 50 or 20 teeth before the first synchronization pulse S) has stopped. In the example of Figure 2 is the Crankshaft 20 teeth before the first synchronization pulse S stopped. Therefore, if after 28 teeth starting detection E (ie 20 teeth after the first pre-injection I4) already the first synchronization pulse S has occurred (which is in the Example of Figure 2 is the case), it can be seen that the crankshaft 20 teeth before the synchronization pulse S. had stopped. As soon as the synchronization pulse S has occurred is, the internal combustion engine is synchronized, and Thus, a defined order of the after the synchronization pulse S pre-injectors from the central Control unit 1 can be determined.

As can be seen from the diagram of FIG achieved that all pre-injectors I1 to I4 ago the opening of the associated inlet valve E1 to E4 or at least at the beginning of the opening process (inlet valve EV4) be dropped off; be discontinued; be deducted; be dismissed. Thus, all Vorabeinspritzer on the Participate in combustion, so that the pollutant emissions by unburned expelled fuel not greater than at a start with sequential injection operation. There an ignition in the four cylinders at the earliest possible time allows this pilot injection strategy a quick start of the internal combustion engine.

The diagram of Figure 3 corresponds to that of Figure 2, except of that at the time of the starter E the camshaft signal CAM is high and the internal combustion engine 50 (± 7) teeth of the crankshaft sensor before the first Synchronization pulse S has stopped. Since at the time the start detection E the camshaft signal CAM high is the first cylinder group of the cylinders 1, 2 and the second cylinder group formed by the cylinders 3, 4. In this case, (after eight recognized and valid Teeth of the crankshaft sensor) only the cylinder 2 with the Vorabspritzer supplied I2, while in the previously known Provided method pre-injector I1 'for the cylinder first is omitted. Since in this example 28 teeth after the Starter ID E has not yet occurred a synchronization pulse S. is, the next or the next pre-injection at a predetermined angular distance to the angular position, on delivered the first pre-injection. As soon as the first synchronization pulse S has occurred, can restore the order of the following pre-injectors from the central control unit 1 in the sequential injection mode be determined.

Claims (6)

1. A method for injecting fuel into a multi-cylinder internal combustion engine, comprising
   at least one injection valve (2) per cylinder (7),
   a camshaft (5) for operating the inlet valves (6), which rotates at half the speed of the crankshaft (8),
   a camshaft sensor (9) supplying a periodic camshaft signal (CAM),
   a crankshaft sensor (4) supplying a crankshaft signal (CRK) representing the crankshaft angle containing a synchronization pulse (S) per crankshaft revolution, and
   a central control unit (1), which controls the injection valves (2) so that during a starting phase they each inject one fuel pilot injection (I) per cylinder (7), and then in the normal sequential injection mode they inject amounts of fuel determined by the control unit (1),
   characterized in that a number of stationary angle positions of the crankshaft (8) at which the internal combustion engine (3) comes to a stop after switching off with the clutch disengaged, equal to the number of cylinders, can be saved in the central control unit (1),
   and that during the starting phase, the cylinders (7) are supplied with the pilot injections (I) one after the other in time depending on the camshaft signal (CAM) and the saved stationary angle positions.
2. The method as claimed in claim 1, characterized in that the camshaft signal (CAM) enables every cycle to be divided into two segments (360°) corresponding to two consecutive crankshaft revolutions (720°), and that depending on the camshaft signal (CAM), the stationary angle positions are divided into two groups, and that the group comprising the current stationary angle position at which the internal combustion engine has stopped is determined.
3. The method as claimed in claim 2, characterized in that, depending on the camshaft signal (CAM), the cylinders are divided into a first and second group, and that, depending on the determined group of stationary angle positions, a cylinder is selected from the first cylinder group to be the first supplied with a pilot injection (I).
4. The method as claimed in claim 3, characterized in that that cylinder of the first cylinder group whose inlet valve is definitely closed or at least predominantly closed, is the first supplied with a pilot injection.
5. The method as claimed in claim 4, characterized in that the angle separation between the crankshaft angle position at which the first pilot injection (I) is discharged and the angle position of the first synchronization pulse (S) is compared with the angle separation between two adjacent saved stationary angle positions, and the sequence of the next pilot injections (I) determined as a function of this comparison.
6. The method as claimed in one of the previous claims, characterized in that after the first synchronization pulse (S) has occurred, the sequence of the remaining pilot injections (I) is defined in sequential mode.

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