Process for controlling an injection valve in a fast-running fuel-injection two-stroke internal combustion engine and device for implementing it

In a method for controlling an injection valve (16) in a high-speed internal combustion engine with fuel injection, in which method, with each revolution of the engine, at a trigger point (TP1,TP2), a trigger signal is generated and according to the trigger signal, the injection operation is initiated, in which, for low engine speeds, the injection start is within a first range (ESB1) of the crankshaft angle of rotation and in which, for high engine speeds, the injection start is within a second range (ESB2) of the crankshaft angle of rotation, which second range (ESB2) in comparison with the first range (ESB1), is displaced in the direction "early" relative to the top dead center (OT), an optimal operating behavior is achieved in that, to each of the two ranges (ESB1 or ESB2), a trigger point of its own (TP1 or TP2) is allocated and in that, when changing between low and high engine speeds, starting from a predetermined threshold engine speed, a changeover of the control between the two trigger points (TP1,TP2) takes place.

SCOPE OF APPLICATION 
The invention relates to a method for controlling an injection valve in a 
high-speed two-stroke internal combustion engine with fuel injection. 
In addition, the invention relates to a device for the performance of such 
a method. 
STATE OF THE ART 
Whereas four-stroke engines in general, over the entire engine speed and 
load range, possess a relatively uniform running of the engine, two-stroke 
engines show significant differences between the engine speed ranges 
(idling) and "operative range". When idling (low engine speed), a 
considerable rough running takes place which always calls for an exact 
injection. When starting from a certain trigger signal, a computation of 
the injection start is effected, the same has to take place in the 
immediate proximity of the trigger signal since otherwise significant 
errors with regard to the desired injection start may occur. These--as 
already mentioned--depend substantially on the degree of uniformity of the 
running of the engine and may differ considerably from revolution to 
revolution so that the running of the engine becomes uncontrollable. That 
is why the injection has to take place close to the trigger point or 
trigger signal. 
As is illustrated in the FIG. 1 in an angle diagram of the engine 
crankshaft (KW) relative to the top dead center (OT), for low engine 
speeds, the injection starts (ESB) in dependence upon the respective 
engine configuration, are within a first (hatched) range (ESB1) between 
180 and 240.degree. KW (angles W4 and W3) before the top dead center (OT) 
of the engine. At higher engine speeds (several revs/min), all other 
injection starts, according to the respective load states, are necessary. 
Usually a displacement of the injection start in the direction of "early" 
within a second (hatched) range (ESB2) is necessary that is located 
between 270 and 350.degree. KW (angles W2 and W1) before the top dead 
center. 
For low engine speeds (e.g. when idling), according to the foregoing 
explanations it is expedient and advantageous to place the trigger point 
at which the trigger signal is generated close to the beginning of the 
first range (ESB1), thus e.g. at the point identified with (TP) in FIG. 1. 
In this way only a short angular distance exists between (TP) and the 
beginning of the injection range (W3). If, with increasing numebrs of 
revolutions, the injection start is brought forward from the range (ESB1) 
into the range (ESB2), in such a case also the trigger point (TP) ought to 
be correspondingly brought forward. A (virtual) displacement of the 
trigger point is expediently carried out in that the computation of the 
injection start for the next revolution is effected (long arrow from TP 
via the angles W5 and W6 of the ignition range ZB after W1 in FIG. 1). On 
account of the requsitite computation time as wella s on account of the 
time required for controlling the opening time of the injection valve, it 
may happen in dependence of the required injection start, that the trigger 
signal (e.g. from a Hall transmitter) employed for the idling range cannot 
be evaluated. The injection for the next revolution would not be possible 
or only subject to serious flaws. 
TECHNICAL PROBLEM, SOLUTION, ADVANTAGES 
The technical problem of the invention is now to state a method for 
controlling a high-speed two-stroke engine, which overcomes these 
disadvantages and ensures for each revolution of the engine in dependence 
upon load and speed an optimal injection start in connection with the 
requisite duration of the injection. 
The technical problem is resolved in a method of the type stated in the 
beginning in that, to each of the two ranges, a trigger point of its own 
is allocated and in that, when changing over between low and high engine 
speeds, starting from a predetermined threshold number of revolutions, a 
changeover of the control takes place between the two trigger points. In 
this manner it is possible, when changing over to higher engine speeds 
and, thereby, to a brought-forward injection start, to switch over to a 
new trigger point optimally adapted to the injection start so that, even 
at higher revs/min, a perfect and optimized control of the injection start 
is possible. 
A first preferred embodiment of the method according to the invention is 
distinguished in that the two trigger points are in each case located 
within a trigger range which, in relation to the crankshaft angle of 
rotation, is close to the associated injection range. The effects of 
engine speed fluctuations on the injection control are limited to a 
minimum hereby. 
It has turned out to be especially advantageous if, according to a further 
development of this embodiment, the first range of approximately 
180-240.degree. KW is located before the top dead center (OT) of the 
engine, the second range within approximately 270.degree.-350.degree. KW 
before the top dead center, the first trigger range (within approximately 
180 through 270.degree. KW before the top dead center and the second 
trigger tange is within approximately 10-150.degree. KW before the upper 
dead center. 
A further preferred embodiment of the method according to the invention is 
characterized in that the ignition of the engine is effected with the aid 
of an ignition magneto of more than 10.degree. KW, more particularly 
approximately 20.degree. KW, before the top dead center, and in that the 
ignition signal emitted by the magneto is used as trigger signal for the 
second injection range. An overlapping of computation time, injection 
duration and trigger point is avoided with certainty. 
The device for performing the method according to the invention is 
characterized in that the device comprises a control section which, by 
means of a change-over switch controlled by the control section is 
optionally connectable to one of the two trigger signal transmitters and 
in that an output of the control section is operatively connected with the 
injection valve. 
Further embodiments result from the dependent claims.

DETAILED DESCRIPTION OF THE INVENTION AND BEST WAY OF REALIZING THE 
INVENTION 
In FIG. 2 the changes become apparent which result by the invention in an 
angle diagram according to the FIG. 1. One sets out once again from two 
ranges ((ESB1 and ESB2) of the injection start which extend from the angle 
W4 (180.degree. KW) through W4 (240.degree. KW) and from angle W2 
(270.degree. KW)through W1 (350.degree. KW) before the top dead center. In 
addition to the first trigger point (TP1), which may be located within a 
first trigger range (TB1) of W4 through W1, a second trigger point (TP2) 
is now provided which may be located within a second trigger range (TB2) 
between W6 and W7. In this case, W6 is approximately 10.degree. KW before 
the top dead center. If, setting out from the idling, the revs/min of the 
engine are increased, the injection control is, from a certain threshold 
number of revolutions from the first triggering point (TP1) within the 
first trigger range (TB1) changed over to the second trigger point (TP2) 
within the second trigger range (TB2). The angular divergence between 
trigger point and injection start is shortened thereby, whereby the 
influence of engine speed fluctuations on the injection control is 
minimized. 
A simple embodiment example of a control means for performing the method is 
schematically depicted in FIG. 3. 
The control means 10 comprises a central control section (with 
microprocessor or the like) which, via a controlled change-over switch 13, 
optionally receives trigger signals for controlling the injection start 
from two trigger signal transmitters 11 or 12. The first trigger signal 
transmitter 11 is in this case allocated to the first trigger point (TP1), 
the second trigger signal transmitter 11 is allocated to the second 
trigger point (TP2). The control section is in principle capable od 
deriving the engine speed information necessary for the changing over from 
the sequence of the trigger signals. However, in many cases it will be 
expedient to make provision for a separate engine speed transmitter 15, 
which transmits the engine speed values to the control section 14. The 
output of the control secion 14 is connected with the injection valve 16, 
whose opening start and opening duration can be controlled. 
The first trigger signal transmitter 11 can be a Hall transmitter or a 
similar crank angke sensor which is placed at a pertinent point on the 
engine. The second trigger signal transmitter 12 could, with engines 
equipped with magnet wheel/fan wheel and integral magnet for controlling 
the ignition, be this magnet itself. In other engine configurations this 
task could likewise be assumed by a further Hll transmitter. 
This econd trigger signal transmitter 12 or trigger point (TP2) should--as 
already mentioned--be located within an angle range of approximately 
10-150.degree. KW before the top dead center. In standard high-speed 
two-stroke internal combustion engines, as are also made use of in manual 
operation equipment produced by the applicants, the ignition magnet is, in 
the form of a trigger signal transmitter, located approximately 20.degree. 
KW before the top dead center (OT). Consequently, an overlapping of 
computtation time/injection duration/trigger point is avoided. With this. 
for each engine revolution, in dependence of load and engine speed range, 
an optimal injection start in connection with the necessary injection 
duration is ensured. 
Altogether, with the invention, a method and a device for controlling 
high-speed two-stroke internal combustion engines with fuel injection are 
obtained which guarantee that the internal combustion engine possesses, 
within the entire engine speed range, an optimal operational behavior 
manifesting itself in performance running, in pollutant emission as well 
as in a uniform running of the engine. 
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Control system 10 
trigger signal transmitter 
11, 12 
change-over switch 
13 
control section 14 
engine speed transmitter 
15 
injection valve 16 
injection start range 
ESB1, ESB2 
top dead center 0T 
trigger range TB 
trigger ranges TB1, TB2 
trigger point TP 
trigger points TP1, TP2 
ignition range ZB 
angles W1-W7. 
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