U.S. patent number 3,720,193 [Application Number 05/133,597] was granted by the patent office on 1973-03-13 for method and apparatus for coding and reading data governing the duration of energization of fuel injection in an internal combustion engine.
This patent grant is currently assigned to Societe des Procedes Modernes d'Injection Sopromi. Invention is credited to Louis A. Monpetit.
United States Patent |
3,720,193 |
Monpetit |
March 13, 1973 |
METHOD AND APPARATUS FOR CODING AND READING DATA GOVERNING THE
DURATION OF ENERGIZATION OF FUEL INJECTION IN AN INTERNAL
COMBUSTION ENGINE
Abstract
An arrangement for coding and reading data representing the
duration of fuel injection in an internal combustion engine
comprising a pulse generator, such as a transparent cylinder driven
by the engine shaft and on which are recorded a plurality of series
of points distributed in accordance with a hyperbolic law and each
series corresponding to pulses to be generated for a predetermined
position of the power-controlling means such as the throttle valve
in the input manifold of the engine. A detector is shifted under
the control of said power-controlling means across said series of
points so that at each revolution of the pulse generator a
corresponding series of points is detected and transformed into a
series of pulses, the interval of time between the pulses depending
on the spacing of the points and on the speed of rotation of the
said pulse generator, the detected pulses being transformed by a
discriminator into a rectangular pulse, the width of which is
dependent on the intervals between the detected pulses. The
rectangular pulse is utilized to energize an electrically
controlled fuel supply system for the duration of said rectangular
pulse.
Inventors: |
Monpetit; Louis A.
(Etang-la-Ville, FR) |
Assignee: |
Societe des Procedes Modernes
d'Injection Sopromi (Les Mureaux, FR)
|
Family
ID: |
8642292 |
Appl.
No.: |
05/133,597 |
Filed: |
April 13, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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774362 |
Nov 8, 1968 |
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Foreign Application Priority Data
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Nov 27, 1967 [FR] |
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67129744 |
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Current U.S.
Class: |
123/477; 123/494;
123/490 |
Current CPC
Class: |
F02D
41/32 (20130101); F02D 29/00 (20130101); F02D
2700/07 (20130101) |
Current International
Class: |
F02D
29/00 (20060101); F02D 41/32 (20060101); F02m
051/06 () |
Field of
Search: |
;123/32AE,32EA,119R,139E |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Parent Case Text
RELATED APPLICATIONS
This application is a continuation-in-part of my earlier filed
copending application, Ser. No. 774,362 filed Nov. 8, 1968 and now
abandoned.
Claims
What I claim is:
1. An electrical fuel injection control system for supplying
rectangular energizing signals to electromagnetic fuel injectors
for internal combustion engines, the duration of the rectangular
signals being a function of at least one operating parameter,
wherein the improvement comprises:
a. means for generating pulses to control the duration of each
injection period, said pulse generating means including a moving
surface, the speed of the surface being a function of the engine
speed and the surface having a series of spaced detectable elements
arranged thereon to pass a fixed reference point located in
proximity of the surface, the spacing between successive adjacent
elements increasing in the direction opposite to the direction of
movement of the surface;
b. sensing means disposed at the reference point for producing a
short pulse in response to passage of each element past the sensing
means; and
c. means responsive to the time intervals between short pulses from
the sensing means to generate a rectangular injection signal for as
long as the time intervals between pulses are less than a
predetermined reference time interval.
2. The control system of claim 1 wherein the means responsive to
the time intervals between short pulses for generating a
rectangular signal comprises:
a. first means responsive to the time interval between the first
and second pulses in the series of pulses having the shortest time
interval therebetween to initiate the rectangular signal and
b. second means responsive to the first time interval between a
subsequent pulse and the next preceding pulse that is longer than
the reference time interval to terminate the rectangular
signal.
3. The control system of claim 1 wherein the spacing between
successive elements in each series increases according to a
hyperbolic law, whereby the duration of injection for a given
position of the sensing means is approximately constant regardless
of engine speed.
4. The control system of claim 1 wherein the spacing between
successive elements in each series increases according to a
hyperbolic law modified by experimental operating data, whereby the
duration of injection for each position of the sensing means varies
with engine speed by an amount predetermined by the experimental
data.
5. The control system of claim 1 further comprising means for
moving the sensing means in response to at least one engine
operating parameter to a plurality of reference points located on a
line transverse to the direction of movement of the surface, the
sensing means responding at each reference point to a corresponding
series of elements arranged to pass the reference point.
6. The control system of claim 5 wherein the elements of each
series are connected in continuous lines to corresponding elements
of series on adjacent paths scanned by the sensing means to permit
smoothly continuous movement of the sensing means in response to
said at least one engine parameter without interrupting the
generation of pulses by the pulse generating means.
7. The control system of claim 5 wherein the means for moving the
sensing means comprises a power-controlling means for the internal
combustion engine.
8. The control system of claim 5 wherein the engine is a
spark-ignition engine, and the means for moving the sensing means
comprises a throttle-control means for the engine.
9. The combination set forth in claim 1 wherein the moving surface
of said pulse generating means comprises a cylinder, and said
sensing means comprise a light-sensitive means.
10. The combination set forth in claim 5 wherein the moving surface
of said pulse generating means comprises a cylinder rotating in
synchronism with the engine, and said detectable elements comprise
lines inscribed on the surface of said cylinder.
11. The combination set forth in claim 10 wherein said sensing
means comprises light responsive apparatus disposed with respect to
said cylinders so that a pulse is produced each time one of said
lines passes said sensing means as said cylinder rotates in
synchronism with said engine.
12. The combination set forth in claim 11 wherein said means for
moving said sensing means comprises means for moving said light
responsive apparatus longitudinally with respect to said
cylinder.
13. The combination set forth in claim 11 wherein said light
responsive apparatus comprises a source of infrared rays and a
detector in registry with said source disposed outside said
cylinder.
14. The combination set forth in claim 11 wherein said light
responsive apparatus comprises a source of visible light disposed
within said cylinder and a light sensitive semiconductor in
registry with said source disposed outside said cylinder.
15. In an internal combustion engine comprising an electrically
controlled fuel supply system energized by a rectangular signal for
the duration of said signal, the method of coding and reading data
for controlling the duration of said rectangular signal in
accordance with engine operating parameters, comprising the steps
of:
a. experimentally determining the fuel requirement characteristics
for said engine as a function of two engine operating parameters
one of which is the engine speed;
b. recording said fuel requirement characteristics on a
two-dimensional surface as a series of indicia;
c. moving said surface past shiftable sensing means responsive to
the presence of said indicia at a speed dependent on the rotary
speed of said engine, said sensing means scanning in any of its
positions those of the indicia situated on a common line along the
direction of movement of said surface;
d. producing a pulse each time one of said indicia moves past said
sensing means;
e. initiating a rectangular signal in response to at least the
pulse produced by the first of said series of indicia; and
f. terminating the rectangular signal as a function of the time
interval between two succeeding pulses generated by the series of
indicia; and
g. applying said rectangular signal to said electrically controlled
fuel supply system.
16. The method set forth in claim 15 wherein:
a. said characteristics are recorded as a plurality of series of
points along circumferential substantially parallel lines on a
hollow transparent cylinder, each series of points corresponding to
a predetermined value of one of the engine operating parameters as
a function of engine speed;
b. corresponding points in each of said series are joined together
to form a plurality of lines in a direction substantially different
from the direction of movement of the surface of said cylinder;
and
c. said cylinder is rotated so that said surface passes between a
light source and light sensitive means to produce a pulse each time
one of said lines crosses the area between said source and said
light sensitive means.
17. The method set forth in claim 15 including the further step of
shifting said light source and light sensitive means in a direction
parallel to the longitudinal axis of said cylinder as the value of
one of said engine operating parameters changes.
18. In a system for intermittently supplying fuel to an internal
combustion engine in response to a rectangular signal, the amount
of fuel supplied being proportional to the duration of the signal,
the method of coding and reading data for controlling the duration
of the rectangular signal comprising the steps of:
a. experimentally determining the fuel requirement characteristics
for said engine as a function of engine speed and at least one
other engine operating parameter;
b. transforming said fuel requirement characteristics into
corresponding fuel supply duration times as a function of the
operating parameters;
c. recording a series of increasingly spaced detectable elements
corresponding to each value of said other operating parameter on a
surface, the spacing of said elements being such that for
preselected velocities, related to corresponding engine speeds, of
movement of the surface relative to a reference point in a
direction opposite to the direction of increasing element spacing,
the times for passage of all elements in the series that are spaced
more closely than spacings at said velocities corresponding to a
fixed reference time interval are equal to the fuel supply duration
times determined in step (b);
d. moving said surface at said velocities as a function of engine
speed in a direction opposite to the direction of increasing
element spacing past the reference point;
e. producing a pulse in response to movement of each one of said
detectable elements past the reference point;
f. initiating a rectangular signal in response to a time interval
between said pulses less than the fixed reference time interval;
and
g. terminating the rectangular signal in response to a time
interval between said pulses at least equal to the fixed reference
time interval.
Description
BACKGROUND OF INVENTION
The present invention has for an object a method and means for
coding and reading information concerning the duration of injection
for internal combustion engines provided with electromagnetic
injectors, energized by a rectangular electric pulse, the duration
of which is proportional to that of the injection and depends
therefore on the speed of rotation of the engine and on the means
controlling the power of the engine.
It is a known fact that the duration of injection may be adjusted
with reference to a single fundamental parameter provided for
adjustment, such for instance as the air pressure in the
inlet-manifold of a spark ignition engine, the adjustment being
corrected thereafter to take into account a number of auxiliary
parameters such as the temperature of the engine, altitude and the
like. Now, in certain cases, such as for minimizing air pollution,
it is necessary to simultaneously rely on two independent
fundamental parameters. Two parameters which may be used are the
speed of rotation of the engine and the position of the means
controlling the engine power, generally the angular position of the
throttle valve controlling the flow of air through the
inlet-manifold, or the absolute pressure in the inlet-manifold.
Such an adjustment may be obtained as well known in the art by a
tridimensional cam cooperating with a cam follower adapted to
modify the duration of injection in accordance with the speed of
rotation of the engine, said cam follower being shifted along a
line parallel with the rotary axis of the cam by means of a
connection controlled by the angular position of the throttle valve
in the inlet-manifold. However, said prior technique is
comparatively expensive since the points of the corresponding
tridimensional curve when found and experimentally marked for one
type of engine must be worked out so as to provide means for
designing the three-dimensional cam and the reproduction of such a
cam is rather expensive. Furthermore, the transformation of speed
into angular movement is not an easy matter and cannot be
accurately reproduced by reason of friction and the like.
It has also been proposed to electronically incorporate a
correction with a single regulating parameter, the pressure drop in
the admission pipe as a function of the speed of rotation, but such
a correction remains always approximate and its accuracy depends on
the complexity of the circuits employed.
The present invention thus has as a further object the elimination
of such drawbacks.
SUMMARY OF INVENTION
The present invention covers a method of coding and reading data
for controlling the duration of energization of an electrically
controlled fuel supply system as a function of two independent
variables, one variable being the rotary speed of the engine, the
other being for instance the position of the means controlling the
engine power. The duration is coded in form of a plurality of
series of points, each series corresponding to a predetermined
position assumed by the means controlling the engine power. The
series of points are recorded in a pulse generator revolving at a
speed proportional to the rotary speed of the engine. The pulses
generated by the recorded points are detected and fed into a
discriminator which transforms them into a rectangular pulse for
controlling the energization of said electrically controlled fuel
supply system.
The rectangular pulse begins when the pulse or pulses generated by
the beginning of the series of points are fed into the
discriminator and it terminates when the interval of time between
two generated pulses is greater than a predetermined reference
duration.
To obtain a constant duration of the rectangular pulse
independently of the rotary speed of the engine, the spacing
between the points in a series, starting from the first points, has
to increase gradually in accordance with a hyperbolic law.
By recording the points in a series with spacing in accordance with
another law, one can obtain a duration of the rectangular pulse
which can be any function of the speed at which the pulse generator
is revolving and hence, of the rotary speed of the engine. The law
of spacing can be obtained from the experimentally determined
function corresponding to the particular type of engine
involved.
The pulse detecting means is controlled by the means controlling
the engine power so as to be transversely shifted with reference to
the direction of the circumferential movement of the pulse
generator. Consequently each position of the power controlling
means, is associated with one series of points recorded in the
pulse generator.
Furthermore, each point of a series of points is associated with
the corresponding point of the adjacent series so that the
associated points may be joined to form uninterrupted lines. It is
thereby possible to produce the generated pulses for any position
of the means controlling the engine power.
The arrangement for the execution of the above-disclosed method
comprises a pulse generator constituted for instance by a
cylindrical drum which rotates in synchronism with the engine. The
drum is transparent and carries on its surface dark lines extending
substantially parallel to the rotary axis of the drum. The spacing
of the lines corresponds to the spacing of the pulses detected by a
pulse detector, the position of which is controlled by the shifting
of the means controlling the engine power. An electronic
discriminator is provided to transform the detected pulses into a
rectangular pulse.
The detector of said arrangement may advantageously be constituted
by a source of infra-red rays housed in the drum and associated
with a receiver formed by a highly sensitive photodiode or
photo-transistor located outside the drum and facing the source of
light.
Furthermore, the power-controlling means for the engine may be
constituted by the throttle valve controlling the admission of air
into the engine.
DESCRIPTION OF DRAWINGS
The following description given by way of example and with a view
to furthering the understanding of the invention is illustrated in
the accompanying drawings wherein:
FIG. 1 shows three curves each defining the amount of fuel q to be
injected as a function of the speed of rotation N of the engine for
a different position of the power-controlling means of the engine,
constituted in the example chosen by the angle .theta. by which the
throttle valve is open to allow admission of air;
FIG. 2 is a diagrammatic view of the system including the engine
equipped with the improved regulating arrangement according to the
invention;
FIG. 3 is a perspective view of the pulse generator and of the
detector associated therewith;
FIG. 4 shows the outer developed surface of the pulse generator
whereon the corresponding pulse generating points are distributed
in accordance with a hyperbolic law;
FIG. 5 is a view similar to FIG. 4 where the pulse generating
points are distributed in accordance with another law;
FIG. 6 is a diagrammatic illustration of the method for
transforming the curves according to FIG. 1 into a certain
distribution of the points;
FIG. 7 illustrates a schematic diagram of one part of of the
discriminator circuit;
FIG. 8 illustrates the voltages at different points in the diagram
of FIG. 7;
FIG. 9 illustrates a schematic diagram of another part of said
discriminator circuit; and
FIG. 10 illustrates the voltages at different points in the diagram
of FIG. 9.
DETAILED DESCRIPTION OF INVENTION
Turning to FIG. 1 of the drawings, it is apparent that according to
the angle .theta.1, .theta.2, .theta.3 assumed by the throttle
valve in the inlet manifold, the amount of fuel q to be injected
and consequently the duration of injection t are a function of the
speed of rotation of the engine. The curves illustrated are
obviously drawn in an arbitrary manner, but they correspond
substantially to the shape of the curves found experimentally. If a
large number of said curves is drawn, there can be obtained a
surface illustrating the amount of fuel to be injected as a
function of two independent parameters, to wit: the speed of
rotation N and the angle .theta. assumed by the throttle valve in
the inlet manifold.
In FIG. 2 there is illustrated schematically an engine 4 with its
electronic injection system including the inlet manifold 10 with
the throttle valve 11 controlled by the accelerator pedal. The
electromagnetic injectors 5 are fitted in the inlet manifold, but
this type of arrangement is not essential. A high pressure pump 7
driven by an electric motor 6 sucks fuel out of the container 8 and
feeds it under pressure into the injectors 5 through the pipe
9.
A source of voltage 15 feeds a discriminator 14 which receives
pulses from the pulse generator 1 through the detector 13 and
transforms said pulses into rectangular pulses which are fed to the
injectors 5 through distributor 16 and the leads 17 in accordance
with the sequence of ignitions required. Detector 13 is operatively
connected with the accelerator pedal 12 whereas the pulse generator
1 revolves with the engine shaft. An example of the generator is
illustrated in FIG. 3 where it is shown as constituted by a
transparent cylinder 1 operatively connected through its carrier
shaft 4 with the output shaft of the engine. Said cylinder 1
carries on its peripheral surface a network of dark lines 3
distributed in a manner such as to transmit through the detector 13
pulses spaced in accordance with a characteristic curve defining
the amount of fuel to be injected for a predetermined position of
the throttle valve or the like power-controlling means, as a
function of engine speed. In the example illustrated, a luminous
source 18 is provided which acts on the detector 13 constituted for
instance by a very sensitive photo-diode or photo-transistor 19. It
is, of course, possible to resort to similar arrangements insuring
very high accuracy of cut-off such as a source of infra-red rays.
Of course, the cylinder 1 may be opaque and provided with
transparent lines formed therein.
The principle of the improved adjusting method according to the
invention is consequently as follows: If constant quantity of fuel
is supplied to the engine for a given position of the throttle
valve, whatever may be the speed of rotation, the curves .theta.1,
.theta.2, .theta.3 (FIG. 1) would be horizontal lines and the
duration of injection would be constant throughout the range of
rotary speeds. Considering now FIG. 4 which shows the surface of
the cylinder 1 illustrated in FIG. 3 in a developed condition, it
is apparent that said surface carries a plurality of series of
points 2. Each series corresponds to a different opening angle
.theta. of the throttle valve. Corresponding points in said series
of points are joined by lines 3, as shown, and generate pulses in
the detector which transmits them to discriminator 14 adapted to
transform said pulses which are of very short duration into
rectangular pulses controlling the injectors. The discriminator 14
can be designed for instance in a manner such that the rectangular
pulse commences with the first two generated short pulses and
terminates when the time elapsing between two successive generated
short pulses is longer than a predetermined reference time T.sub.R,
as will be described hereinafter.
If it is desired to obtain a constant duration of injection without
regard to engine speed, the spacing between the points should
increase in accordance with the above-described hyperbolic law,
since the spacing between two points corresponds to the angle by
which the motor revolves during a time which is inversely
proportional to the speed of rotation of the engine. Consequently,
in order to obtain a substantially constant time interval between
the pulse commencing the rectangular pulse and that terminating it,
the spacing between the corresponding points and consequently the
rotary angle corresponding thereto should increase proportionally
with the rotary speed. With such an arrangement, there is therefore
obtained a constant duration of injection, whatever may be the
speed of rotation of the engine. Said method of regulation is
applicable for instance to Diesel engines. In such a case, the
detector 13 would not be connected with a throttle valve located in
the inlet manifold, but with the power-controlling means of the
engine, which generally, in the case of a Diesel engine, is the
speed governor.
However, for all spark ignition engines, the curves defining the
injection period are not constituted by horizontal lines, but
rather have a shape such as that illustrated in FIG. 1.
Consequently, each curve corresponding to a predetermined angle
.theta. is illustrated by a corresponding series of points 2 on the
cylinder 1. Since said curves are experimentally defined for a
finite number of positions of the throttle valve, there is
initially obtained only a finite number of series of points 2.
However, with a sufficient number of series of points 2, it is
possible to achieve a valid interpolation for any position whatever
of the detector 13 and it is sufficient therefore to connect
corresponding points in the series of points 2 by lines 3 such as
those illustrated in FIGS. 3, 4 and 5.
Taking as an example the series of points shown in FIG. 5 for the
angle .theta.3, it can be seen that when the engine is rotating
relatively slowly, for instance at idle speed, the time interval
between generated pulses may exceed T.sub.R between the 100th and
101st recorded points, resulting in termination of the injection
pulse. However, when the speed of rotation increases, it can be
seen that a time interval between generated pulses exceeding
T.sub.R, may not occur until one of the more widely spaced recorded
points such as the 107th or 108th in the series is reached by the
pulse detector. The time interval in both cases, between the first
point and the point determining the end of injection will be
approximately the same since the rotational angle traversed on the
surface of the cylinder until the recorded point which terminates
the injection pulse is reached, increases in proportion to the
rotational speed.
Turning now to FIGS. 7 to 10 it can be seen that the discriminator
comprises three elements: a bistable multivibrator producing the
rectangular injection signal when triggered into its first stable
position by a first circuit which produces the triggering signal
when it receives two succeeding pulses at the beginning of each
injection cycle and a second circuit which produces a signal which
triggers the bistable multivibrator into its second stable
position.
The first circuit (FIG. 7) comprises an input A' connected to the
base of transistor T'1 via a resistor R'4. The collector of said
transistor T'1 is connected to a point B' via a transistor R'3
while its emitter is connected to ground and to the base via
resistor R'5. Point B' is connected to the emitter of unijunction
transistor T'2, to ground via capacitor C'1 and to the voltage
supply via resistor R'1. The bases one and two of said unijunction
transistor T'2 are connected respectively to ground via resistor
R'7 and to the voltage supply via resistor R'6. A transistor T'3 is
arranged with its collector-emitter circuit between the voltage
supply and ground via resistor R'8, while is base is connected to
base one of the unijunction transistor T'2. Furthermore the
collector of said transistor T'3 is connected to the base of
transistor T4 via capacitor C2. Said transistor T4 is connected
with its collector-emitter circuit between the voltage supply and
ground via resistor R9, and its base is connected to capacitor C2
as already indicated and to the voltage supply via resistor R2.
Point F' is connected to the voltage supply via resistor R10, to
the collector of transistor T4 via diode D1, to input A' via diode
D2, and to the base of transistor T5 via diodes D3 and D4 connected
in series to provide thermal compensation. The base of said
transistor T5 is moreover connected to ground via resistor R12
while the collector-emitter circuit of said transistor T5 is
arranged between the voltage supply and ground via resistor R11,
the output of said first circuit being constituted by the collector
of said transistor T5 which is connected to the input E1, of a
bistable multivibrator of a known type.
As already said, the element (FIG. 7) which triggers the bistable
multivibrator for the beginning of the injection comprises an input
A' at which the pulses from the pulse generator 13 (FIG. 2) are
applied. Each pulse causes the transistor T'1 to become conductive.
This causes the capacitor C'1 to be discharged, and the potential
at B' falls to zero. Therefore, the unijunction transistor T'2
becomes nonconducting. At the end of the very short pulses at A',
transistor T'1 becomes nonconducting, and the potential at B' rises
up to a certain value depending upon the characteristics of the
unijunction transistor T'2. When this value is reached, the
unijunction transistor T'2 triggers, discharging capacitor C'1 to a
very low value as indicated in FIG. 8. Transistor T'3 is conductive
each time the unijunction transistor T'2 is conductive, which means
that the potential at C' is low when said transistor T'3 is
conductive and high when it is nonconducting.
As indicated in FIG. 8 we have at A' a series of pulses, causing at
B' an evolution of the potential as indicated, during which period
we have at C' a rectangular signal of the same duration. Each time
transistor T'3 becomes conductive, capacitor C'2 is discharged,
meaning that the potential at D' goes down to a value corresponding
to the negative terminal of the source of current and then goes
slowly up as the capacitor C2 is charged through resistor R2.
During this period transistor T4 is nonconductive, which means that
the potential at E' is positive. Transistor T5 constitutes,
together with the diodes D1 and D2, a NAND gate, which means that a
negative signal at E1 is obtained only if a positive signal is
present both at E' and A'. This condition is fulfilled each time
the pulses 1, 2 or 3 for instance are sufficiently close so that
the signal at E' is not yet terminated when another signal at
appears A'.
Actually the transistor T5 is conductive when the signal applied to
its base via the diodes D3 and D4 is positive, that is to say when
both the points A' and E' are at a positive potential. The pulses
numbered 1, 2 and 3 are the very first pulses produced at the
beginning of each injection cycle, and they are necessarily very
close, as described below. The pulse numbered n+1 is the last one,
and it should be noted that the distance separating pulses n+1 and
1 is much greater than indicated.
The negative signals at E1 are applied to the corresponding input
E1 of the bistable multivibrator triggering it so that it produces
at its outputs a rectangular pulse energizing the fuel supply
system during its duration.
The signal applied to the other input E2 of said bistable
multivibrator to stop the injection is produced by the device shown
in FIG. 9. As one can see, its structure is identical to that of
the left half of the circuit shown in FIG. 7 and it works in the
same way. The only difference is that the time constant of R1 C1 is
much longer than that of R'1 C'1 (FIG. 7). In fact the time
constant R1 C1 = T.sub.R is chosen such that the potential reached
at B is lower than the critical value which causes the unijunction
transistor T2 to be triggered, as long as the time interval
separating two succeeding pulses i-4, i-3, for example, is less
than this time constant. But when this time interval exceeds the
time constant T.sub.R as shown between pulses i1 and i, the
unijunction transistor T2 is triggered, transistor T3 becomes
conductive and a negative signal appears at C which is applied to
the second input E2 of the bistable multivibration, causing the
rectangular pulse to disappear.
Obviously the spacing of the points or lines connecting such points
should be such that the adjustment may be substantially a
continuous one. Thus, preferably the duration of the reference time
T.sub.R should be less than 1 percent of the minimum injection time
and, conversely, the cutoff frequency should be at least equal to
10.sup.5 cycles per second. This very close spacing may be
obtained, for instance, through a photographic reproduction of the
lines 3 on the cylinder 1.
It should be realized that the transparent cylinder may be
replaced, for example, by a disc on which the program is recorded
magnetically on a plurality of tracks. The same arrangement may
furthermore serve for automatically controlling, with a suitable
family of lines 3, the advance of the ignition.
The spacing between the points of a series of points as a function
of a given curve t (N) for a given value .theta. of the
power-controlling means can be obtained by a suitable
transformation of the curve t(N). FIG. 6 illustrates such a
transformation of the curve t (N,.theta.3). It can be seen that for
any value of the rotary speed of the engine N there is an angle A
on the pulse generator defined by the duration of injection t in
accordance with the equation:
(1) A = k .times. N .times. t
thus, A5 = k .times. N5 .times. t5 (with the incorporation of a
multiplying coefficient k to adjust the dimensions) for the speed
N5 illustrated in FIG. 6. The value of the said angle is shown on
the axis OA at the point A5. The product of this multiplication can
easily be obtained by means of the straight line N5, its slope
being given by k .times. N5, in following the arrows. The
geometrical construction on FIG. 6 allows one to determine the
spacing a between two points of a series of points around the value
A. According to the above description, a must be such that at a
given speed of the engine, e.g. N5 the interval of time between the
pulses increases to approach T.sub.R as a limit. That means
(2) a = k .times. N .times. T.sub.R
or for N5, a5 = k .times. N5 .times. T.sub.R
This multiplication can be made by means of a straight line k
.times. T.sub.R as shown on FIG. 6, its slope being given by the
value of k .times. T.sub.R. As indicated by the arrows, each point
of the curve a (A) can easily be obtained.
Obviously the invention is by no means limited to the examples
disclosed and its features may be applied singly or in combination
as required without widening the scope of the invention as defined
in the accompanying claims.
* * * * *