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.

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.

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.

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.