EP0912825B1 - Method of controlling the injection process in a high-speed 2-stroke fuel injection internal combustion engine - Google Patents

Abstract

The invention concerns a method of controlling the injection process in a high-speed 2-stroke internal combustion engine (11). According to the invention, the internal combustion engine (11) comprises first means (12) for generating one trigger signal per revolution, said signal being fixed with the angle of rotation, for controlling injection, and second means (13) for generating alternating voltage which is dependent on the speed of rotation and whose period is a fraction (1/n) of the time per revolution (revolution time) of the 2-stroke internal combustion engine (11). A simple electronic injection-control arrangement having optimum injection parameters which can be calculated precisely for all speeds of rotation is attained in that, in addition to the trigger signal, the alternating voltage generated is additionally used to control the injection process.

Description

Technical field

The invention relates to a method for controlling the injection process in a high-speed 2-stroke internal combustion engine with fuel injection, which 2-stroke internal combustion engine has first means for generating an angle-fixed trigger signal per revolution for the injection control and second means for generating a speed-dependent AC voltage, the period of which is a fraction (l / n) of the time per revolution (revolution time) of the 2-stroke internal combustion engine.

State of the art

From EP-A1-0 688 951 it is known to provide an injection control for small, compact four-stroke engines without a battery, in which an electromagnetic injection valve is actuated by voltage pulses, which are arranged on a flywheel and co-rotating permanent magnets in a vicinity of the flywheel fixed coil arrangement can be induced. While the start of injection is fixed by the position of the coil arrangement, the injection duration is limited by a time control circuit after a calculated period of time by interrupting the injection valve circuit. The problems that occur when interrupting such an injector circuit are described in EP-B1-0 543 826.

While four-stroke engines generally have a relatively uniform engine running over the entire speed and load range, two-stroke engines show considerable differences between the "idling" and "working range" speed ranges. When idling (low engine speeds of a few 100 rpm), there is considerable run-out, which always requires an exact injection. If, based on a specific trigger signal, a calculation of the start of injection is carried out, this must take place in the immediate vicinity of the trigger signal, since otherwise considerable errors can occur with regard to the desired start of injection. As already mentioned, these depend essentially on the degree of uniformity of the engine running and can differ considerably from revolution to revolution, so that the engine running becomes uncontrollable. The injection must therefore also take place in the immediate vicinity of the trigger point or trigger signal.

As shown in FIG. 1 in an angle diagram for the engine crankshaft (KW) in relation to the top dead center (TDC), the injection starts (ESB) for low engine speeds are in a first (hatched) area depending on the respective engine configuration ( ESB1) between 180 and 240 ° KW (angle W4 and W3) before the top dead center (TDC) of the internal combustion engine. At higher speeds (several 1000 rpm), different starts of injection, depending on the respective load conditions, are required. It is usually necessary to shift the start of injection towards "early" into a second (hatched) area (ESB2), which is between 270 and 350 ° KG (angles W2 and W1) before top dead center (TDC).

For low engine speeds (e.g. at idle) it is according to the above Practical and advantageous explanations to place the trigger point at which the trigger signal is generated close to the beginning of the first area (ESB1), e.g. at the point designated by (TP) in Fig. 1. In this way there is only a short angular distance between (TP) and the beginning of the injection area (w3). If the start of injection is advanced from the area (ESB1) to the area (ESB2) with increasing engine speeds, the trigger point (TP) should actually be moved accordingly. A (quasi) shift of the trigger point is expediently carried out by carrying out the calculation of the start of injection for the next revolution (long arrow from TP over the angles W5 and W6 of the ignition range ZB to W1 in FIG. 1). Due to the required computing time and the time required to control the opening time for the injection valve, depending on the required start of injection, the trigger signal used for the idling range (e.g. a Hall sensor) cannot be evaluated. As a result, the injection for the next revolution would not be possible or would only be possible with a high degree of error.

An electronic control of the injection quantity in a diesel engine is known from IT publication "ISATA" No. 87 008. The injection control uses a trigger signal that is fixed at the angle of rotation and identifies the TDC point of a cylinder and a common speed signal. If the speed sensor fails, the system switches to a speed signal that is supplied by a conventional alternator.

From EP-A2-0 434 111 a method and a device for setting the injection time in a 2-stroke internal combustion engine are known, in which the top dead center by a first scanned marking (54) on the crankshaft and the angle of rotation of the crankshaft Teeth (52) arranged and scanned evenly distributed over the circumference of the crankshaft can be precisely determined and the injection can be controlled by a connected computer. However, special markings and sensors are required for this, which require considerable effort during installation. In addition, manufacturing tolerances of the sensor devices are not sufficiently taken into account when determining the angle.

The correction of such inaccuracies by arithmetic means is described in EP-A1-0 583 495, but it is also assumed there that a special sensor wheel connected to the crankshaft is used, so that the problem of the design effort remains.

Finally, EP-A2-0 066 758 proposes the use of a magneto generator to derive an angle signal for the angle of rotation of the crankshaft of an internal combustion engine. However, this magneto generator is a generator specially and exclusively adapted for measuring the angle of rotation, which is accommodated in a very special way in the ignition distributor of the machine and is therefore unsuitable for simple machines and for retrofitting, both in terms of expenditure and space.

Presentation of the invention, task, solution, advantages

It is an object of the invention to provide a method for controlling the injection of a high-speed two-stroke engine, which overcomes these disadvantages without changes to the internal combustion engine itself and ensures an optimal start of injection in connection with the required injection duration for each revolution of the internal combustion engine as a function of load and speed.

The object is achieved in a method of the type mentioned by the features from the characterizing part of claim 1. By using the AC voltage with its periodicity, additional reference points can be provided during the revolution without changing the internal combustion engine, to which the injection control system can refer.

A first preferred embodiment of the method according to the invention is characterized in that values of the angle of rotation associated with the individual periods of the alternating voltage generated are derived, which angle of rotation values are used together with the trigger signal for injection control. In this way, almost equidistant angle marks can be generated, which allow optimal control of the injection process at different and fluctuating speeds.

A further preferred embodiment of the method according to the invention is characterized in that for the correct assignment of the angle of rotation values to the periods of the alternating voltage in the case of fluctuations in the length of the individual period durations which are constant over time, for example due to manufacturing tolerances or the like, the individual period durations are measured, a correction factor for each period is determined from the ratio of the measured period to the theoretical period, each of which is a fraction (l / n) of the revolution time, that a relative corrected angle of rotation value is assigned to each period using the associated correction factor, and that under Reference to the angle of rotation fixed Trigger signal, the relative corrected rotation angle values are converted into absolute corrected rotation angle values, which are used for injection control. By determining the correction factors, it is possible to correct manufacturing-related irregularities without changing the internal combustion engine.

If, according to another preferred embodiment, to compensate for fluctuations in the length of the period durations, in particular caused by speed fluctuations and / or phase shifts in the AC voltage, the correction factors are determined and stored several times in succession, and statistically averaged correction values are formed from the stored correction values and are used for To assign the relative corrected rotation angle values to the period durations, the influence of short-term changes on the determination of the correction factors can also be largely eliminated.

Further embodiments result from the dependent claims.

Brief description of the drawings

Fig. 1

ein auf die Kurbelwellendrehung bezogenes Winkeldiagramm mit den Steuerwinkel für eine herkömmliche Einspritzsteuerung mit einem Triggerpunkt,

Fig. 2

in einem Blockschaltbild eine beispielhafte Vorrichtung zur Durchführung des Verfahrens nach der Erfindung,

Fig. 3

mehrere Zeitdiagramme zur Erläuterung der Vorgehensweise beim Bestimmen der Drehwinkelwerte nach dem erfindungsgemäßen Verfahren, und

Fig. 4

einen Programmablaufplan für die Berechnung der Korrekturwerte beim Verfahren nach der Erfindung.

The invention will be explained in more detail below on the basis of exemplary embodiments in connection with the drawing. Show it

Fig. 1

an angle diagram related to the crankshaft rotation with the control angle for a conventional injection control with a trigger point,

Fig. 2

a block diagram shows an exemplary device for performing the method according to the invention,

Fig. 3

several time diagrams to explain the procedure for determining the angle of rotation values according to the method according to the invention, and

Fig. 4

a program flow chart for the calculation of the correction values in the method according to the invention.

Best way to carry out the invention

2 shows an exemplary device for carrying out the method according to the invention in a block diagram. The control device 10 is associated with a high-speed 2-stroke internal combustion engine 11, on which an ignition 12 and a generator 13 for generating a periodic alternating voltage are arranged in a speed-coupled manner. The ignition 12 comprises, for example, a rotating ignition magnet, which generates a suitable ignition signal in a fixed coil, which is available as a trigger signal which is fixed in terms of the angle of rotation for the injection control. The periodic alternating voltage from the generator 13 and the trigger signal from the ignition 12 are applied to suitable inputs of a microcontroller 15, which cooperates with a non-volatile memory for storing calculated correction values and controls an injection valve 14 for the 2-stroke internal combustion engine 11 with one output.

The basis for the method according to the invention is now the provision of the fixed periodic trigger signal (TS), which - as already mentioned - can be generated in connection with the ignition 12 already present and is generated as a single pulse per revolution (see FIG. 3c) . Furthermore, the generator 13, e.g. a generator flanged to the machine 11 is used, which emits a certain number n of sine waves per revolution of 360 ° KW (n-10 is assumed in the further explanation; see FIG. 3a). From these sine waves, pulses can be derived (see Fig. 3b), which (for n-10) have an angular distance of 36 °. The generator pulses are fed to the microcontroller 15, which also receives the fixed trigger pulse (TS) from the ignition 12. From these pulses, the microcontroller 15 not only realizes the mathematical calculation of the injection quantities (start of injection, injection duration), but also has the ability to perform an angle correction of the 36 ° pulses. This correction is necessary because the pulse intervals or period durations are subject to errors due to manufacturing tolerances and phase shifts due to electrical loads on the generator. It should be noted here that the computer must use other parameters such as temperature, load signal, etc. to determine the start of injection or the injection duration, so that these variables are to be understood as the result of a corresponding calculation.

The fixed trigger pulse (TS) (FIG. 3c), which serves as a reference variable in this system, is used as the mathematical basis for the correction of angular errors. If the microcontroller 15 recognizes that the If the internal combustion engine 11 is in the operating speed range in which the degree of uniformity of the internal combustion engine is greatest, the main program, which calculates the injection quantities for the current revolutions, is briefly exited, as shown in the self-explanatory program flow chart of FIG. 4.

Speed measurements begin in all 36 ° angle windows. The synchronization of the internal combustion engine is constantly checked. The time windows (period durations of the generator pulses) are measured in the angle windows. If the synchronism error of the internal combustion engine has been recognized as being sufficiently small, the time window measurement (period measurement) is significant, i.e. the measured values can be used.

The summation of the times in the time windows gives the true time for a speed. The sub-windows must therefore be exactly 36 °, i.e. 10% of the total rotation time. Each window is now provided with a correction factor, and the correction factors, 10 in the present example, are written into the non-volatile memory 16. It is also marked that a correction measurement has been made.

The microcontroller 15 now returns to the main program, where it calculates this routine again at a predetermined interval. The new correction factors are processed statistically in each case with the correction factors previously calculated and stored in such a way that ultimately n (here: 10) statistical ones There are mean values for the deviation of the 36 ° window from the uniformity, in such a way that these correction factors converge to the real value as the engine running time increases. This procedure enables the microcontroller to react to the manufacturing tolerances of the generator 13 and to generate certain correction factors which tell "him" how large the individual angular sections determined by the periodic pulses are in reality.

The arithmetic assignment of the angle window to top dead center (OT) or to the fixed trigger pulse (TS) is based on the creation of a time window between the trigger pulse (TS) and the following pulse from the generator 13, in predetermined individual revolutions of intermittent time intervals. Based on the calculated speed, the microcontroller 15 calculates the time difference between these two successive pulses and thus calculates the absolute correction based on the top dead center (TDC).

For the calculation of the injection target values, the microcontroller 15 accesses predefined specifications from the engine map, which are stored in a map control. The microcontroller 15 adapts the stored characteristic map sizes to its calculated angle sizes and thus controls the injection valve 14 in a self-correcting manner.

Overall, the invention results in an electronic possibility which, in a simple manner and without fundamental technical revision of the design of 2-stroke internal combustion engines, delivers optimal, precisely calculable injection parameters.

Reference symbol list:

Control device

10th

2-stroke internal combustion engine (high-speed)

11

Ignition (first means)

12th

Generator (second means)

13

Injector

14

Microcontroller

15

Memory (non-volatile)

16

Start of injection area

ESB1, ESB2

Top Dead Center

OT

Trigger range

TB

Trigger point

TP

Trigger signal (trigger pulse)

TS

Ignition range

Eg

angle

W1 - W6

Claims (6)

1. A method for controlling the injection process for a high-speed two-cycle internal combustion engine (11) with fuel injection, this two-cycle internal combustion engine (11) showing first means (12) for generating a trigger signal (TS) for a fixed angle of rotation per revolution for the injection control as well as second means (13) for generating an alternating voltage depending on the number of revolutions, the period of which is a fraction (I/n) of the time per revolution (time of revolution) of the two-cycle internal combustion engine (11),
   characterized in
   that additionally the generated alternating tension is used besides the trigger signal (TS) for the control of the injection process and that the second means comprise a heating generator (13) which is placed on the two-cycle internal combustion engine (11) and which is driven by the engine and that corresponding values of the angle of rotation are derived from the individual periods of the generated alternating voltage, rotation angle values which are used with the trigger signal (TS) for the injection control.
2. A method according to claim 1,
   characterized in
   that for the correct correspondence of the rotation angle values to the periods of the alternating voltage for time constant fluctuations in the length of the individual periods, determined for example through process tolerances or the like, the individual periods are measured, a coefficient of correction is determined for each period from the ratio of the measured periods to the theoretical periods which constitute respectively a fraction (I/n) of the time of revolution, that a relative corrected rotation angle value corresponds to each period by applying the corresponding coefficient of correction and that, with reference to the trigger signal (TS) for a fixed angle of rotation, the relative corrected rotation angle values are converted into absolute corrected rotation angle values which are used for the injection control.
3. A method according to claim 2,
   characterized in
   that, for compensating time-variant fluctuations in the length of the periods, caused in particular by fluctuations of the number of revolutions and/or by phase shifts in the alternating voltage, the coefficients of correction are determined and stored several times consecutively, and correction values, the mean of which is statically taken, are formed from the stored correction values and are used for the correspondence of the relative corrected rotation angle values to the periods.
4. A method according to any of the claims 2 and 3,
   characterized in
   that the measuring of the individual periods takes place in the operative r.p.m. range of the two-cycle internal combustion engine (11), that during the measuring actions the synchronism of the two-cyle internal combustion engine (11) is continuously supervised and that the measured values are only evaluated when the synchronism error during the measuring actions is situated under a predetermined value.
5. A method according to any of the claims 1 to 4,
   characterized in
   that for the injection control a microcontroller (15) is used which, subject to the trigger signal (TS) and to the generated alternating voltage, reads out the corresponding characteristic diagramm parameters from a characteristic diagramm control and uses them for the control of an injection valve (14).
6. A method according to any of the claims 1 to 5,
   characterized in
   that the first means comprise the ignition (12) of the two-cycle internal combustion engine (11).