EP0683855B1 - Fuel injection control device for an internal combustion engine - Google Patents

Abstract

In the fuel injection control device described, immediately after the engine has been started up, the position of the crankshaft and camshaft is determined. This is achieved either by means of an absolute transmitter system or by identification of the stopping point, with the angular position of the crankshaft or camshaft being memorized when stationary. Immediately after the engine has been restarted, fuel is injected into an open inlet valve in the appropriate phase. On commencement of rotation, further injections are triggered into one or several open or still closed inlet valves. Once correct synchronization has been achieved, the control device switches over to normal injection.

Description

State of the art

The invention relates to a device for controlling the fuel injection in an internal combustion engine.

In multi-cylinder internal combustion engines with electronic injection, the control unit usually calculates when and how much fuel is to be injected per cylinder. So that these calculations can be carried out correctly, the respective position of the crankshaft or camshaft of the internal combustion engine must be known, it is therefore common and is described, for example, in EP-PS 0 017 933, that the crankshaft and the camshaft are included are each connected to a disk, on the surface of which at least one reference mark is applied, a plurality of similar markings, also called increments, being additionally applied to the crankshaft disk.

The two rotating disks are scanned by suitable fixed transducers. A clear statement can be made from the chronological sequence of the pulses delivered by the transducers win the position of crankshaft and camshaft and corresponding control signals for injection or ignition can be formed in the control unit.

The known system has the disadvantage that a clear position detection is only possible after a certain rotation of the two shafts, since for this position detection the passage of the reference mark or the reference marks at the respective sensors must be waited for. This means that correct injection cannot take place immediately after the engine is started.

It is therefore proposed in the as yet unpublished German patent application P 42 30 616, which relates to a device for recognizing the position of at least one shaft having a reference mark, to use this device in an internal combustion engine and to do so after switching off the ignition and injection To carry out run-out detection, the position of the crankshaft and camshaft being determined and stored by the control unit when it is at a standstill. When switched on again, the position determined in this way is immediately available to the control unit, so that the first injections can take place shortly after the start of rotation. In the device described in P 42 30 616 it is stated that injections should take place as early as possible, but it is not explained in more detail how these injections are precisely defined.

From JP-A-60 062 665 a device for regulating an internal combustion engine is known, in which the crankshaft position is stored in the control unit when it is at a standstill and this position is used to control the ignition when the engine is restarted.

Advantages of the invention

The device according to the invention with the features of claim 1 has the advantage that the position of the camshaft or crankshaft in the control unit is known immediately after the internal combustion engine is switched on, so that it can begin immediately with the cylinder-correct assignment of the injection, the first injection already can take place before the start of rotation, so that the internal combustion engine starts up particularly early.

After the start of rotation, but before the synchronization, further injections can be carried out in the correct cylinder, which further improve the run-up.

The transition between the start injections and the normal injection is advantageously designed in such a way that neither missing nor double injection takes place in or for a cylinder, thereby ensuring that all cylinders are supplied with fuel uniformly and no leaning or over-greasing of the Mixing takes place in individual cylinders.

drawing

The invention is illustrated in the drawing and is explained in more detail in the following description. 1 shows a rough overview of the arrangement of the crankshaft or camshaft together with the associated sensors and the control unit, in which the calculations for controlling the injection run. In FIG. 2, control signals or signals registered by sensors are plotted over time during the starting phase of an internal combustion engine.

Description of the embodiment

In Figure 1, the components of an internal combustion engine required to explain the invention are exemplified. In this case, 10 denotes an encoder disk, which is rigidly connected to the crankshaft 11 of an internal combustion engine and has a multiplicity of similar angle marks 12 on its circumference. Besides these A reference mark 13 of the same kind is provided, which is realized, for example, by two missing angle marks.

A second encoder disk 14 is connected to the camshaft 15 of the internal combustion engine and has a segment 16 on its circumference, with which the phase position of the reference mark on the crankshaft disk is determined. The connection between crankshaft and camshaft, which rotates the camshaft at half the crankshaft speed, is symbolized by 17.

The illustrated shape of the encoder disks connected to the crankshaft or camshaft is exemplary and can be replaced by other selectable shapes.

The two encoder disks 10, 14 are scanned by sensors 18, 19, for example inductive sensors or Hall sensors, the signals generated in the sensors as the angle marks pass are either processed in the same way and fed to a control unit 20 or only in a suitable manner in the control unit, where, for example, rectangular signals are formed, the rising edges of which correspond to the start of an angle mark and the falling edges of which correspond to the end of an angle mark. These signals or the time sequences of the individual pulses are further processed in control unit 20.

The control unit 20 receives, via various inputs, further input quantities required for the control or regulation of the internal combustion engine, which are measured by various sensors. Examples of such sensors are mentioned: a temperature sensor 21, which measures the engine temperature, a throttle valve sensor 22, which detects the position of the throttle valve, a pressure sensor 23 which measures the pressure in the intake pipe or the pressure in a cylinder of the internal combustion engine. Furthermore, an “ignition on” signal is supplied via the input 24, which signal is supplied by the terminal K115 of the ignition lock when the ignition switch 25 is closed.

On the output side, the control unit, which includes computing or storage means (not shown) and a permanent storage designated 30, provides signals for the ignition and injection for corresponding components of the internal combustion engine, not specified. These signals are emitted via the outputs 26 and 27 of the control unit 20.

Depending on requirements, further sensors can be used, the signals of which are fed to the control unit, and the control unit 20 can also emit further signals required for regulating the internal combustion engine. It is also not necessary that all of the sensors shown are present.

The control unit 20 is supplied with voltage in the usual way with the aid of a battery 28, which is connected to the control unit 20 via a switch 29 during operation of the internal combustion engine and during a run-on phase after the engine has been switched off.

With the device described in Figure 1, the position of the two shafts 11, 15 can be detected at any time during operation of the internal combustion engine. Since the assignment between crankshaft and camshaft is known as well as the assignment between the position of the camshaft and the position of the individual cylinders, synchronization can take place after recognition of the reference mark and, after synchronization has taken place, the injection and the ignition are controlled or regulated in a known manner will. Such control of an internal combustion engine is described for example in DE-OS 39 23 478 and is therefore not explained in more detail here.

With the device described in FIG. 1, however, recognition of the motor position in the run-down during the so-called run-on phase is also possible. In this wakeup phase, which is going on The normal operation of the internal combustion engine, which is known, for example, from the aforementioned publication, is followed by an evaluation of the sensor output signals; the last determined positions of the crankshaft and camshaft are stored in the permanent memory of the control unit and are therefore immediately available when the engine is switched on again. The exact procedure is described in DE-P 42 30 616.

In Figure 2 for a four-cylinder internal combustion engine essential for understanding the invention signal or. Voltage curves U (t) [v], which were recorded during test runs, are plotted against the time t in milliseconds. FIG. 2a shows the control signals A, B, C and D emitted by the control unit for the injection valves of cylinders 1 to 4, the injections being characterized by the minima. The ignitions that take place in the individual cylinders are symbolized by an arrow, area X denotes the opened cylinder inlet valves.

In Figure 2b, the upper signal E indicates the course of the ignition signals, the lower signal F is the output signal of the camshaft sensor or the phase sensor, the minimum occurring every 720 ° KW.

In Figure 2c, the control signal G for the electric fuel pump relay and the speed signal H and the output signal I of the crankshaft sensor are plotted.

At time t = 0, the start of the internal combustion engine is initiated via the ignition lock 25. At time t1, control unit 20 applies voltage to the individual systems or transmitters, and the electric fuel pump relay is actuated so that the fuel pump begins to deliver fuel. Since the control unit 20 already knows the exact angular position of the crankshaft or the camshaft at this point in time, it can immediately start calculating the times that are important for the injection.

At time t2, the starter is engaged; due to the large current consumption, there is a drop in signals A to E. From time t2 the engine begins to turn, the crankshaft encoder emits speed-dependent pulses, at time t3 the reference mark is recognized, later, at higher speeds, the occurrence of the speed signals at the resolution selected in FIG. 2 can no longer be recognized.

After the first minimum of the phase signal is recognized, the regular synchronization can take place and the normal SEFI takes place.

In the example shown in FIG. 2, the injection valve EV3 is the first to be open, and the control unit can trigger a first phase-correct injection before the engine begins to rotate. This first injection is designated NS and is also called zero splash, since the speed is still zero and takes place in an open intake valve. The zero splash can be triggered, for example, after the control unit reset, it can be triggered with the first speed signal or when the starter is engaged. The engagement of the starter can be recognized by the resulting voltage drop or by the starter terminal K150 itself.

A prerequisite for this zero splash is that the necessary fuel pressure is already present in the fuel rail. If the internal combustion engine has not been switched off for too long or is still in the after-running phase, the required fuel pressure is usually still present, so that a zero splash can be emitted under these conditions.

From time t2, the engine begins to rotate, thereby opening other injectors. In the example according to FIG. 2, this is the injection valve EV4. Even before the internal combustion engine has been synchronized, the control unit triggers further injections, which are referred to as the first sprayer ES. In the case of EV4, these first splashes ES take place in the open inlet valve, in EV 1 they are placed in front of the opening of the inlet valve. This ensures that the first cylinder, which can be ignited after synchronization, already contains an ignitable mixture and that the engine already starts to run here, which means a shortening of the starting time.

After synchronization has taken place, the control unit switches to normal injection, for example to the known SEFI injection. At the same time, the necessary ignitions are then triggered by the control unit, so that the internal combustion engine has reached its normal operating state.

The transition from the start injection to the normal injection is designed in such a way that there is no missing or double injection into the individual cylinders. The control unit can take temperature-dependent parameters into account when calculating the injection quantity.

If the engine has been switched off for a long time so that the fuel pressure has dropped sharply, no fuel will be injected with the zero sprayer, but the two first sprays can take place because at this point the fuel pump has already built up a fuel pressure sufficient for injections. In this case, a considerable improvement in the speed ramp-up is likewise obtained with the method according to the invention.

In the worst case, the position of the crankshaft and camshaft stored after the run-on has ended does not match the actual position, so that the wrong injectors are activated in the start-up phase before synchronization, which leads to a deterioration in the speed ramp-up compared to the correct control, which corresponds to the speed ramp-up then the speed ramp-up to be achieved in systems without injection before synchronization.

Claims (3)

1. Device for controlling the fuel injection in an internal combustion engine with a computing device in which the angle position of the crankshaft and/or camshaft is evaluated in order to form control signals for the injection valves, the position of the crankshaft and/or camshaft being determined up to the stationary state in the computing device during a running-on phase after the ignition of the internal combustion engine is switched off and the position being stored in the stationary state and being used directly after the internal combustion engine is switched on in order to form the control signals for a first injection into an open inlet valve or before an open inlet valve even before the engine begins to turn, and further injections into open or before closed inlet valves of other cylinders being triggered after the start of turning but still before synchronization has taken place, and a transition to a customary cylinder-specific injection taking place after the synchronization.
2. Device according to Claim 1, characterized in that the computing device is the control device of the internal combustion engine, to which control device the signals of the sensors are fed, which signals sense the crankshaft or camshaft or discs connected to these shafts, and further signals, in particular an "ignition-on" signal.
3. Device according to Claim 1 or 2, characterized in that a sensor disc which is assigned to the one shaft of the internal combustion engine has a reference mark which is detected by evaluation of the sensor signals in the computing device, a synchronization being triggered after the reference mark is detected by the computing device.

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