US 3587552 A
Description (OCR text may contain errors)
United States Patent Inventor Bernard Varaut Dravell, France Appl. No. 780,046 Filed Nov. 29, 1968 Patented June 28, 1971 Assignee Compagnie Des Compteurs Paris, France Priority Nov. 30, 1967 France 130310 AUTOMATIC ADVANCE ELECTRONIC IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINES 6 Claims, 6 Drawing Figs.
3 1 5/209 hit. F02p 3/02 Field 01 Search 123/148,
. References Cited UNITED STATES PATENTS 2,446,671 8/1948 Short et a1. 123/148E 2,918,913 12/1959 Guiot 123/148E 3,202,146 8/1965 Short et al. l23/148E 3,277,875 10/1966 Miki 123/148E 3,361,123 1/1968 Kasama et al 123/148E Primary Examiner- Laurence M. Goodridge Attorney-Pierce, Scheffler and Parker ABSTRACT: The electronic automatic ignition advance adjustment device for internal combustion engine comprises conductor elements spaced out and moved by said engine depending on its rotation speed, an electromagnetic probe P detecting the passage of said conductor elements, an oscillating assembly connected to said probe, an ignition coil connected, on the one hand, to at least one spark plug of said engine and to said oscillating assembly, and means for modifying the time for setting up the stable oscillatory rating of said oscillating assembly in agreement with the speed of the engine.
" sum 1 UF 3 Y INVENTOR Bernard Van-Gut to H234 PATENTEDJuuzs 1974 SHEET 3 [1F 3 INVENTOR zVQ 4 Bernard Var-nut WM? PAL Aiiorne AUTOMATIC ADVANCE ELECTRONIC IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINES The present invention has for its object a device enabling an automatic ignition advance in internal combustion engines, particularly for motor vehicles, characterized in that it enables a zero ignition advance to be obtained for very low rotation speeds of the engine shaft, this advance increasing when the speed of said shaft increases up to a certain value, beyond which the advance remains practically constant.
The automatic ignition advance of the invention essentially comprises a metal cam or similar device integral with the engine shaft and comprising a projection, said cam cooperating with a pickup made by a detector coil surrounding a magnetic core, a coil whose excess voltage coefficient variations caused by the passing of the projection of the cam in front of the coil of the pickup, when the cam rotates, are used for modifying the amplitude of the oscillations of a resonant circuit electronic oscillator. Pickup, called proximity" and detecting the passage of electrically conducting objects, have already been described in French Pat. No. 1,482,206 and it is with reference to a pickup of this kind that the device according to the invention is described in that which follows.
In a pickup, according to French Pat. No. 1,482,206, in the absence of any metal part in the vicinity of the magnetic core surrounding the detector coil of the pickup, the excess voltage coefficient of the resonant circuit is at its maximal value, and the pickup oscillates. If a metal part is brought near to said magnetic core, the excess voltage coefficient diminishes, and, as from a certain value, the oscillations stop and the pickup is arrested. When the metal part is removed from the magnetic core, the excess voltage coefficient progressively increases and, as soon as it reaches a certain predetermined value, the oscillations recommence and finish up by becoming stable.
According to the present invention, means have been devised for causing the time taken by the oscillations to vary and to reestablish themselves in a stable manner in the pickup circuit when the projection of a metal cam rotatively driven by the shaft of an internal combustion engine, is withdrawn from the magnetic core of the pickup, these means having the object of obtaining an ignition advance curve which will show a zero value of the ignition for very low rotation speeds of the shaft of the engine, and a value which increases progressively when the speed of said shaft increases up to a certain value, beyond which the advance becomes practically constant.
An embodiment of the invention is shown, in the attached drawing, by way of nonrestrictive example.
FIG. 1 is a diagrammatic perspective of an internal combustion engine comprising the device according to the invention.
FIG. 2 is an ignition advance curve as a function of the rotation speed of the engine shaft, this curve being obtained by the device of the invention.
FIG. 3 is a diagram-block showing the assembly of the device of the invention.
FIG. 4 is a detailed circuit diagram of an embodiment of the ignition device according to the invention.
FIG. 5 is a curve showing the time variations for effecting oscillation as a function of the various parameters.
FIG. 6 is a view in elevation showing a modified embodiment of the conductor element mounted on the flywheel of the engine which controls the oscillator.
In FIG. 1, there is shown diagrammatically a four-cylinder engine 1 in each of which a piston 2 slides whose connectingrod 3 is jointed at its foot on one of the crankpins 4 of the crankshaft 5 rigidly attached to a flywheel 6 and also to a distributing device 7 which is functions direct, in a given order, the current pulses produced from the device of the invention, designated on the whole by 8, towards each spark-plug 9. The device 8 is, in this example, connected to a probe P which forms part of it and functions to detect the successive passage of the two circumferentially spaced arcuate conductor elements II and I2 carried by the flywheel 6. In this manner, two current pulses are produced setting up two sparks by two distinct plugs for each revolution of the crankshaft 5, as would be the case for a four-cylinder engine operating according to a four-stroke cycle.
In that which follows, the angle a of ignition advance is obviously the angle existing at the moment when the spark is produced between the position of one ofthe crankpins of the crankshaft and that which it then assumes when the piston to which it is attached is at top dead center corresponding to the end of the compression stroke of the fuel mixture contained in the cylinder.
FIG. 2 shows the shape of the ignition advance curve as a function of the rotation speed of the crankshaft 5 that is obtained according to the invention, i.e. the curve u=f(N), N being the abovementioned rotation speed. As shown by this curve, the ignition advance must be zero or almost zero in the curve section 0A corresponding to a speed comprised, for instance, between 0 and N, where N, is equal to 500 rpm, so that starting the engine is specifically facilitated when it is cold, seeing that the curve rapidly increases in its ABC section, i.e., up to a rotation speed N where N, is equal, for instance, to 3,000 rpm, which approximately corresponds to the maximum torque rating, this ignition advance then remaining in the CD section, appreciably constant and corresponding, for instance, to an angle a=35.
In FIG. 3, the circuit X designates a tuned oscillator which receives, at its input, data coming from a probe P detecting the passage of the conducting parts 11, 12 of the flywheel 6, whereby said parts 11 and 12 function as a switch interrupting the oscillations of the oscillator at a rate which depends upon the speed of the engine. For a better understanding of that which follows, only the conducting part 11 is shown.
As shown in FIG. 4, the probe P comprises a winding I. and a magnetic core 13 forming a self-inductance which may have various shapes, for instance, that of an airgap magnetic circuit. The core 13 is placed in the vicinity of the rotary path of the conducting parts 11 and 12.
It is presumed in that which follows that the crankshaft 5 and hence the flywheel 6 revolve in the direction of the arrow The oscillator X is connected by an output to an amplifier W leading to a monostable flip-flop 2 which also receives a variable voltage coming from a frequency to voltage converter Y so that said flip-flop Z allows-0r does not allows-the current to pass coming from a supply source S towards a control device 0 of the ignition coil R supplying the distributor 7.
In FIG. 4, the coil L of the probe P forms with a condenser C, an oscillating circuit whose resonance frequency has for its value Arr LC,. C, is a linkage condenser which forms a counterreaction loop with a counterreaction resistance R,, connected, on the one hand, to a top A of the coil L, and, on the other, to the emitter of a transistor T. A diode D, rectifies at the point B the alternating voltage coming from the oscillating circuit L-C,. A condenser C filters the output current of the transistor T. Resistances R and R, as well as a diode D form a polarization circuit of the base of the transistor T.
A terminal S of the circuit described above is connected up by means of a resistance R to one of the poles of a direct voltage source S, which is the accumulator battery of the motor vehicle for instance, whose other pole is connected to the earth M of said vehicle.
T designates a transistor whose collector, by means of a resistance R, is connected up to the input terminal I of the oscillator X described above, whereas its emitter is connected up to the other input terminal N which is the earth connection of said oscillator X.
The base of the transistor T is connected to the converter Y, which itself is connected by a conductor 14 to the output 15 of the monostable flip-flop Z. The converter Y comprises a condenser C, and a resistance R, which are parallely mounted between the earth M and conductor 14, downstream of a diode D, thus forming the biasing for the base circuit of transistor T. In this way, the frequency of the signals coming from the monostable flip-flop 2 as explained in that which follows, is converted into a voltage which depends from this frequency to make the transistor T' pass, or not.
The input 16 of the monostable flip-flop Z is connected to the output of the amplifier W whose input is connected to the output S terminal of the oscillator X. As shown in the drawing, the amplifier W comprises a transistor T, whose base is connected to the output S of the oscillator X, the emitter-collector circuit of this transistor being connected by a condenser C, for coupling to the input 16 of the monostable flip-flop Z. A diode D is advantageously provided, being interposed between the condenser C and the earth M, so that only one of the amplified alternates of the oscillator X is applied to the input of the monostable flip-flop Z.
The monostable flip-flop Z which comprises the commonemitter transistors T and T and associated in a known manner to a condenser C comprises a second output 17 connected to a control circuit Q for the ignition coil.
The circuit Q is made under the form of an amplifier incorporating transistors T,, T, mounted in tandem on the terminals of the source S, the emitter-collector circuit of the second transistor T,,, which is a power transistor, incorporating the primary of the coil R whose secondary is connected to the distributor 7 of FIG. 3.
During the passage of the conducting part 11 in front of the coil L of the-probe P, the oscillator X is obviously blocked, so that its output voltage is zero. During the rest of the revolution of the flywheel 6, the oscillator X oscillates and thus supplies output pulses which are converted after amplifying in the amplifier W by the monostable flip-flop Z into square waves of constant height and length. These voltage square waves are applied by the conductor 14 to the converter Y which converts the succession of these square waves into a voltage which is obviously a function of the rotation speed N of the engine shaft (a function approaching the form: (A-i-B/N). This voltage supplies the base of the transistor T. This transistor is thus passing for speeds N of less than a predetermined value, for instance N,, and is blocked beyond this value.
When the transistor T becomes conductive, it shunts the resistance R, by the resistance R and thus lowers the polarization voltage at the point B, i.e., at the base of the transistor T.
FIG. 5 shows the mean voltage V. the point B, as a time function I, when the conducting part 11 of the flywheel 6 is distant from the coil L, the time origin (t=) being taken as from the moment when the extremity 11a is in the axis of said coil L.
In the time i=0, the polarization voltage V of the base of the transistor T is fixed, on the one hand, for a given value of the source voltage S, by the resistances R R, and R and the diode D and, on the other hand, by a residual discharge voltage that can eventually subsist at the terminals of the condenser C v.,,, is the voltage level v.,, which it is necessary to attain so that the oscillatory rating of the oscillator X is stable. The time t is the time taken by the oscillator X for reaching a stable oscillatory rating, from the time r=o. This time t depends either on the value of the polarization voltage V. or on the slope (tgp) of the oblique straight line v.,,,,v.,,,, or else on these two factors. This slope depends on the values R, and C In actual practice, the values R, and C are determined by the shape and length of the conducting part 11 with a view to obtaining the advance curve of FIG. 2, that is most suited to the type of engine 1, and consequently, R,, and C are fixed, so that the slope 1gp is constant according to the type of engine selected.
One sees in FIG. 5 that if the polarization voltage H increases from the value v.,;,, to the value v.,,,,, the fade-in of the stable oscillatory rating of the oscillator X decreases from t, t
The device shown in FIGS. 3 and 4 works as follows:
When the speed of the engine shaft is low, i.e., less than the value N, (FIG. 2), the transistor T is passing, which shunts the resistance R The polarization voltage v.,,,, is then very slight. There thus follows an increase of the time t required for the stable oscillatory rating of the oscillator X to reached. The ignition spark at the plug 9 occurs at this moment and flashes with a maximum retard which may reach such a value that the ignition advance is zero, as shown in the 0A part of F IG. 2.
When the speed of the engine shaft increases from the value N, TO THE VALUE N the transistor T ceases to be a conductor, and consequently, ceases to shunt the resistance R,. The polarization voltage v.,,,, then increases very quickly. This increase is also added to by the residual voltage of the condenser C which becomes greater and greater as the speed of the engine shaft increases, the discharge time of this condenser then diminishing as a function of this speed. The time t diminishes quickly, which has the result of rapidly increasing the ignition advance.
Beyond the speed N the polarization voltage v. ceases to increase, particularly owing to the fact that the residual ,voltage of the condenser C becomes constant. One then obtains part of the curve CD practically horizontal which corresponds to a constant and maximum angle of the advance of ignition.
As shown by the foregoing, in the example of embodiment shown and described, one has, on the one hand, utilized the properties of an oscillator detecting the passage of a metal part by varying the excess voltage coefficiently i.e. the Quefactor of an induction coil forming part of a resonant circuit, and on the other hand, modified the time for establishing a stable oscillatory rating in said resonant circuit by a means which consists of causing the variation of the polarization voltage of the output transistor of this circuit.
For modifying the time for establishing the stable oscillatory rating in the resonant circuit of the oscillator, one can use, in combination, or otherwise, with the above-mentioned means, means enabling the value of the angle p to be varied, which depends on R, and C by modifying the value of one or both magnitudes as a function of an input voltage of the oscillators circuit, which depends on the speed of the engine shaft. This can be done when it is desired to regulate the engine differently.
For this purpose, one can also vary the distance: probe P, conducting part 11, for instance, by giving an irregular profile to this part, or by at least partially moving said conducting part by the action of centrifugal force, as shown in FIG. 6, where the conducting part 11, is formed by an inertial metal block carried by the flywheel 6 by means of a resilient support 20, the block 11, moving radially outward from the axis of crankshaft rotation, ie in a direction closer to probe P, as the engine speed increases.
1. Electronic automatic ignition advance adjustment device for internal combustion engine comprising conductor elements spaced apart and moved by said engine depending on the rotation speed thereof, the number of said conductor elements being in relation to the number of cylinders of said engine and the thermic cycle thereof, an oscillating assembly comprising a probe composed of a self-inductance and a capacitance in parallel relationship, said assembly being tuned to oscillate in the absence of a conductor element passing in the vicinity whereby the probe may detect the passage of said conductor elements by blocking of the oscillating assembly at each passage of said conductor elements, an ignition coil having two windings, a first winding being connected to at least one spark plug of said engine and a second winding being connected to said oscillating assembly, and means connected to said oscillating assembly for modifying the time for setting up the stable oscillatory working condition thereof in accordance with the speed of the engine so that a spark is produced at said spark-plug only when said stable oscillatory condition is reached, said means for modifying the time for setting up the stable oscillatory condition of the oscillating assembly comprising a monostable flip-flop connected to said oscillating assembly, and a frequency-to-voltage converter also connected to said oscillating assembly at its input and to said flip-flop, so that said flip-flop produces signals at a frequency depending on the rotation speed of the engine and that said converter produces a voltage appreciably inversely proportional to the number of these signals, said voltage thus appreciably inversely proportional to the rotation speed of said engine and applied to the input of said oscillating assembly retarding the setting up of the stable oscillatory working condition.
2. Device as set forth in claim 1 and which further comprises means for adjusting the position of said conductor elements in relation to said probe.
3. Device as set forth in claim 2 wherein said means for adjusting the position of said conductor elements in relation to said probe comprises means resiliently mounting said conductor elements on a rotational element of the engine to effect movement thereof with respect to the axis of rotation of said element as a result of centrifugal force which is itself a function of the rotation speed of the engine.
4. Device as set forth in claim 1, wherein said oscillating as sembly comprises at least one transistor having its emitterbase circuit connected to said probe and biasing resistance in the base circuit, at least one capacitor being provided between said probe and the base of said transistor, said frequency-tovoltage converter comprising at least one output transistor whose collector-emitter circuit is connected to the base of said transistor of the oscillating assembly, whereby the voltage produced by said converter renders said output transistor conductive for a speed below the speed threshold of said engine, said output transistor of the converter then shunting said biasing resistance of the transistor of said oscillating assembly and delaying the setting up of said stable oscillatory rating.
5. Device as set forth in claim 4, wherein said capacitor interposed between the probe and the base of said transistor of the oscillating assembly is adjustable so that the charge to which it is subjected modifies the moment when said stable oscillatory rating is reached 6. Device as set forth in claim 4, further comprising at least one resistance interposed between the probe and the collector-emitter circuit of the transistor of said oscillating assembly whereby the moment of setting up the stable oscillatory working conditions of said oscillating assembly depends on the value of said resistance.