SE447750B - PROCEDURE FOR AUTOMATIC CONTROL OF THE IGNITION OBJECTS OF A COMBUSTION ENGINE AS A DEVICE FOR EXECUTING THE PROCEDURE - Google Patents

Description

10 40 447 750 2 beginning, for example with the help of a piezoelectric transducer such as a predetermined level, modifying the ignition timing in order to emits a signal as the pressure rises the beginning of the second stage shall take place at a specific crankshaft position. One procedure of this kind has the disadvantage of requiring a significant modification of the engine to enable placement of the piezoelectric transducer. In practice, it turns out moreover, difficult to obtain a sufficiently accurate detection of the beginning of the second stage.

During the SAE Congress no. 750 883 in Detroit, Michigan, between On 13 and 17 October 1975, the use of piezoelectric was proposed pressure detectors in the form of rings located between the spark plugs and engine cylinder head. Such donors should give very good results, but in return, changing spark plugs becomes a complicated procedure. MAN must ensure that the donors are not harmed in the slightest at the same time as a full-fledged seal when depositing the new Diocese must be secured. In addition, the electricity corresponding to the ignition sparks can the electrical impulses in some cases cause an impact through or Empty. completely destroy the donors if you do not take safety precautions who take action in connection with the replacement or inspection of the spark plugs an even more delicate process. The present invention has for its object to eliminate the above said inconveniences with the known devices. According to the invention this is achieved by the procedure resp. the device has the characteristics specified in the appended claims. _ The invention and its advantages are more clearly apparent from the following detailed description of an embodiment shown in the accompanying drawing fi ". 1 schematically an engine equipped with a form. In the drawing, g Fig. 2 shows the diagram an electronic circuit for controlling the ignition. Fig. 3 and Z schematically illustrated device according to the invention. 1 shows in more detail the structure of the device shown in FIG. electronic circuit. §Ig¿_§ shows a variant of Fig. 4.

Fig. 1 shows as an example a four-cylinder engine 1 equipped with an electronic ignition circuit designated in its entirety by 3.

This circuit includes a voltage source 3 which supplies a circuit main actually consisting of a capacitor 5 in series with the ignition coil pri- märlindning 9 and of a for the capacitor discharge ínräït fl d fïristor 4 branched from the main circuit. Secondary coil secondary winding feeds in turn each of the engine 1 spark plugs 13, 14, 15 and 16 via an ignition distributor 11, the distributor arm 12 T0ï @ r fl r p UI 40 447 750 in step with the engine crankshaft 17 by means of a drive means (not shown).

In accordance with the invention, the engine is provided with an accelerator. rometer 18 in one piece with the engine cylinder cover 19 and with means for determining at least one reference position of the crankshaft.

The accelerometer 18 and the position detector 20 output data in the form of signals which via the conductors 21 resp. 22 is sent to an electronic 23, which automatically generates a control signal for the ignition circuit and which is fed via a line 24 to the control of the thyristor 4.

Fig. 2 summarizes the most important electronic circuits in the unit 23.

As shown in this figure, they are transmitted by the position detector 20 generated the signals to a circuit capable of generating a signal which is representative of the angular position of the crankshaft. Accelerometerns 18 signal and the signal coming from the circuit 25 is applied to a circuit 26 which emits a signal representative of the angular position of the crankshaft when the pressure is maximum in at least one of the engine cylinders. Last- said signal is compared with a reference or setpoint signal in a circuit 27, in which the control signal for ignition is automatically generated. circle.

The accelerometer 18 can be of any known type and needs not described in detail. In general, it could be made up of one piezoelectric ceramic body and a vibrating mass applied between lan ceramic body parts by means of elastic members.

The means 20, for example a sensor, which is arranged to be fixed set the crankshaft passage past a predetermined reference position, can also be of a known type. In particular, the body could be constituted of an optical detector, such as a photocell, and a disk provided with at least one mark that modifies the detector state at its pass- Suction in front of the detector when the disc rotates. The disc can be fixed load on the crankshaft or, preferably, on a shaft (not shown) as rotates in rotation with the crankshaft and rotates by half the nas speed. Mechanical systems can also be used, such as those that comprises a cam connected to the crankshaft which periodically opens the electric laughs closes a switch.

Fig. 3 shows an embodiment of the electronic circuit , which is supplied from the sensor 20 with a signal consisting of two pulses see I] and Iz whose intermediate ranges are representative of a rotation à fi of the crankshaft. The value of this angle, which is unfortunately, a submultiple is 360 °, but usually at most equal with 3600 depends mainly on the design of the sensor 20. Time interval 9 | a UI # 0 447 750 4 the T between the two pulses is inversely proportional to the the speed N of the shaft 17 and directly proportional to the angle CZK, namely T ÖÜfR / N where T is the time in N, the speed measured in rpm and equal to the average speed for the crankshaft speed during the time interval T and where the CMR finally measured in degrees.

The pulse rate is obviously F = 1 / T.

The signal emitted by the sensor 20 is fed to a first input seconds between the two consecutive pulses walk on an AND frame 29.

An oscillator, for example of the RC type, with the frequency P1 is connected to a circuit 31 for division by K (where K is an integer greater than 1). This circuit 31 is connected via a line 32 to AND the second input of the gate 29, to which it feeds pulses the frequency P3 = F1 / K and whose period time is thus T2 = KT1. Grin- its output 29 is related to the count input C33 of a counter 53 for electrical pulses. The counter 33 may be of a well known type, of the person skilled in the art known as "Type 7493" and manufactured by several manufacturers.

On receiving the pulse II, and more specifically on receiving the entry of the trailing edge 34B of this pulse, emits the circuit 29 at its output the pulses generated by the circuit 31, which in this case will be counted by the counter 33 until the leading edge 34A of pulse I, occurs, i.e. during the time interval between pulses I1 and I2. " The tilting steps in the counter 33 are connected in parallel by conductors. to other independent elements of rocker type 1 a memory circuit 54.

The latter circuit may be of the type known under the name "Type 7474".

The counter 33 is provided with a reset input RAZ33 which are connected to the sensor 20 via a conductor 35 with known delay Means 35A for delaying the leading edges of the pulses I1, I, at reset input RAZ33. g The memory circuit 34 is provided with a charging input Ch3 connected to the sensor Z0 by means of a wire 36.

When the pulse Iz arises after a crankshaft rotation about GKR so under these conditions will cause pulse I, Eramflank 34A transferring the contents of the razor 33, similar to FZ x T, to memory circuit ~ 34, after which the leading edge 33A, which is received by the counter 35 s 447 750 with a certain delay relative to the flank 34A (this delay is shorter than the pulse duration and does not affect the means 35A) brings counter 33 to be reset. This is then ready to register new pulses from the AND gate 29 during a new rotation C axeln.

The memory circuit 34 is provided with output terminals connected to each trigger trigger at a countdown means 37 (for example of pen 74 193).

This means 37 is provided with a countdown input D37 which by means of a line 38 is connected to the output of the oscillating tower 30 for the frequency F1. Circuit 37 is also provided with a terminal Ro37 on which a signal appears at each zero crossing at the countdown device.

The time interval TS required to reset the device 37 - the numerical content of which was originally provided by the circuit 34 and amounts to F, T and to which countdown pulses are applied of the frequency F1 - is defined by the relationship TS - P1 = FZ - T, and the frequency of the zero passages of the member 37 is thus equal to F is here the pulses 11, Iz --- frequency In other words, do K pulses appear on the pin Ros? at countdown the means 37 during the course of each rotation v and the periodicity of these consecutive pulses corresponds to a rotational ning about öíR / K at the crankshaft 17. _ The countdown means 37 is provided with a charge input Ch37 which are connected to terminal RO37 via a conductor 39. During these conditions, each zero-crossing of the body 37 will result in giving a signal on the terminal Ros? and automatically restore this body in charging mode.

The output terminal 37 of the countdown means Ros? is by means of a member re 40 circuit connected to the counting input C78 to a schematic shown contain m pieces of elementary shift registers professionals well known type [for example type 74164) 28, which can circuits of a for comprising eight output terminals, each arranged to transmit a pulse in the form of an "image" of each unit angle of rotation of the crankshaft and of the value IKR / K. The arrangement of these outputs allows a difference of 0 to (Sm-1) pulses emitted by the circuit. ~ b! 01 447 750 6 Each from circuit 3? resulting pulse produces an incremental mental progress of the circuit 28, which emits at any time a signal representative of the number of pulses received during tervallet T '= (sm - 1) rs = (sm - 1) T / K where x 2 sm - 1 The circuit 28, which is an "angle clock", behaves with others words such as a shift register type circuit with Bm output terminals denote from 0 to (Sm - 1) in fiv. 3, which enables tracking of crankshaft rotation step by step within successive angular intervals equal to åh / K with utghgspmüm from a reference position (determined by attachment of the disc provided with the optical marking).

The crankshaft speed is considered constant during that time interval which separates two consecutive pulses I. It is thus obvious that the appropriate choice of the values of than and K allows a lot close monitoring of crankshaft rotation. Usually the values ~ are selected on C ¥ R and K so that the value at an angle of 0 vis Oo 30 'and a few degrees. Circuit 38 may consist of three elements. shift circuits of the shift register type, each with eight output terminals.

The counter 28 has a zero setting terminal RAZ28 which, via a 41 is connected to the counter 20 in such a way as to reset happens for each pulse IT.

The shift register 28 allows selection of an "angle window" whose turnaround and benefits are set out below.

The two outputs of the shift register 28 which correspond to the angular the two angular limits of the window are connected by their respective input clamps. ma with an SR rocker 42.

The flip-flop thus emits a trigger signal between them both angular positions limiting the selected "angle window": trigger the signal starts when a first signal appears on the register 28 output corresponding to the first angular limit of the window (first the state change of the flip-flop 42) and the trigger signal ceases when a second signal appears at the output of the register 28 corresponding to the second angle limit of the year (second change of the condition of the rocker 42).

Fig. 4 schematically shows the structure of the circuits 26 and 27 (compare Fig. 2), which together with the circuit 25 form the electrode níkenheten.

The accelerometer 18 supplies its signal to a low pass filter 44 whose cut-off frequencies are, for example, between 1 H: and some 100 Hz.

The function of the filter is to suppress signals originating from n.

LN UI 40 1 447 750 cylinder head vibrations caused by other phenomena, such as closing of valves, etc. and which usually gives rise to signals of higher frequencies than those resulting from pressure variations inside the engine cylinders. The one of the accelerometers 18 emitted the signal is then integrated into a first integrator 45 and in a second integrator 46. The one provided by the latter integrator the signal supplies a threshold circuit 47 which emits a pulse when the transmitted signal exceeds a maximum value. Circuit 47 pulse signal fed to a first input on an AND gate 48, which - if combined early opening signals are applied to its two other inputs - feeds the pulse signal on to a flip-flop 49. One of the aforementioned both aperture signals come from a logic inverter 50, whose input is connected to the output of the first integrator. When this it is inverted in the inverter to integrator has the output signal zero, a validity or opening signal, which corresponds to the maximum of it the signal emitted by the integrator 46.

At the in fi fl. 1, it has been chosen that one consider the signal part of the other integrator corresponding to the ground pressure in a cylinder C] (Fig. 1). It is obvious that the same phenomenon prevails at the other cylinders and that ignition control one is the same for all cylinders.

For this purpose, the second signal is used as the second opening signal is emitted by the flip-flop 42, which is connected to the circuit 28 (fin. 3) in such a way that this second signal appears only for the determined crankshaft positions when the maximum pressure in the cylinder C1 can is expected to occur during engine operation. For example, one of the rocker 42 inputs connected to the output of the circuit 28 corresponding to the main a first crankshaft position when the piston is in cylinder C1 Its at its upper dead center, while the second input clamp is connected to an output terminal of the circuit 28 corresponding to one second crankshaft position when the crankshaft has moved another 600.

In addition to the signal emitted by the AND gate 48, the flip-flop is supplied 49 with a synchronizing signal which may be the pulses I generated by the sensor 20 when the crankshaft is at a predetermined silent reference mode. This reference mode is selected so that it is occupied of the crankshaft 17 before ignition takes place in the cylinder C1 independently of engine working condition. For example, this reference mode may be located a crankshaft rotation of 650 before the cylinder C1 piston reaches the upper dead center.

Of course, the synchronization signal may be the signal that DI UI 40 447 750 S is emitted by one of the 28 outputs of the circuit, provided that this reference signal in all conditions is generated before the spark spark in cylinder C1.

The output of the rocker 49, which is initially at 0 level, rises to level 1 upon receipt of the synchronization signal and returns to the 0 state upon receipt of a validity signal from the gate 48. This gives a signal in the form of a windows whose size is a function of the angle of rotation of the crankshaft 9 between the reference position and the position when the pressure is maximum in the lindern C1. This signal is fed to a first input on an AND gate 51, which at a second input receives the pulses from the circuit 28 output or the angle clock pulses H. On a third input of circuit 51, the output signal is applied from a flip-flop S2, which is controlled by the synchronizing signal and of the output signal from a counter 53 of shift register type (for example type 74 164). AND gate 51 counts the synchronizing pulses and emits at its output a signal centering a number of n operating cycles of the engine.

Upon the appearance of a first synchronizing signal, the receiver AND gate S1 simultaneously the signal transmitted from flip-flop 49, similar to which is also the signal from the flip-flop 52, which signals constitute the validity signals or opening signals so that the gate 51 allows passage of GK / ܧR pulses originating from the clock H during the entire duration the signal generated by the flip-flop 49. The same phenomenon occurs der n function cycles of the motor, and the cycle counter S3 emits one signal that changes the state of the rocker 52. The number of pulses that pass The gate AND gate 51 is divided by the number of cycles n in the circuit 54, which emits an average of the pulses amounting to rm = 9mK / ¿? R and representing the mean value of the crankshaft rotation that occurred between the passage past the reference position and the position corresponding to the ground pressure in cylinder C1.

These pulses are applied to the countdown terminal D55 of a versible counter 55 (for example type? 4 193) preset pa the theoretical value r of the number of pulses corresponding to it theoretical angular deviation Qth between the reference position of the crankshaft and the position when the pressure in the cylinder C1 is maximum.

The absolute value of the difference rth-rm is representative of the deviation í. = Qth - Gm behavior at circuit S5 is deleted fl å fi klüm ' mother, which are connected to the input terminals of the memory S6 (e.g. Partly of type 74 174), while the sign of the above-mentioned indicated by an output signal which within the Anglo-Saxon language area Y \ 40 = 5 ? com Pth 9 447 750 is called "carry" or "borrow", ie transfer or memory figure in depending on whether the sign is positive or negative. Transferring the information E from the up / down counter 55 to the memory 56 is performed by the pulse generated by the period counter 53 which is delayed by a delay circuit 57a. Same pulse, delayed external in a delay circuit S7b resets the up / down counter S5 to its initial state by means of an input Ch SS. In- the formation E stored in the memory is supplied with an addition-subtraction circuit S8 (Type 7483) to which the theoretical is also applied the value 18th of the angle of rotation of the crankshaft between the the position and the theoretical position where ignition is to occur in cylinder C1, so that the pressure in this cylinder is at a maximum when the crankshaft has rotated an angle Gth with respect to the reference mode.

The circuit 58 supplies a signal which represents the angle "1 2 for the rotation of the crankshaft between the reference position and the actual position at which activation of the ignition in cylinder C1 must occur. This signal is applied to the initialization terminals of an up / down counter 59 (Typ 74 193), whose countdown terminal D59 is connected to the output of an AND gate 60 which receives the synchronization signal at a input terminal and the angle clock signal H at a second input terminal terminal. At zero crossing, the circuit S9 generates at a terminal RO59 circuit 61 to the trigger electrode of the thyristor 4 and to a load or reset terminal Chsg at disconnection S9, thereby allowing reset or reboot. in this an ignition control signal, which is transmitted by a suitable setting the up / down counter 59.

Modifications can be made to the device described above.

For example, it is possible to achieve separate control of the ignition in each of the cylinders of the engine 1 by use as many circuits comprising the circuit elements 48 to 61 which may be required.

In certain conditions during operation of the machine, the ignition be separated from optimal progress over a period of greater or lesser length; for example, if it is desired that the increase in machine temperature shall be faster at start. Generally, an addition subtraction circuit 62 is introduced (which is shown in broken lines in Fig. 4), which changes the value of fi com by algebraically adding a correction 447 750 W value j, between circuits 58 and 59. This change can be made permanently or only temporarily. In the latter case can the duration of the correction may be constant or may again depend on the value assumed by a parameter measured by a detector 63.

Corrections of this kind could just as well be used against knocking phenomenon or to obtain as pure exhaust gases as possible ligt.

It is given that the values rth and ßth in the circuits S5 and 58 must be determined very carefully for each individual engine. Indike- these pre-measured values as a function of motor function the exact state of the tion could be programmed as a function of the same condition.

Pig. 5 schematically shows the apparatus according to the invention. The accelerometer 18 mounted on the engine cylinder head emits a signal to a low-pass filter 44 whose cut-off frequencies, for example is between 1 Hz and a few hundred Hz. This filter has to task of suppressing signals originating from the cylinder head vibrations caused by phenomena such as valve closures, etc and which usually have a higher frequency than the resulting signals of the pressure variations inside the engine cylinders.

The signal emitted by the accelerometer 18 is processed by a integrator 45, the output terminal of which is connected to the input of a logic inverter 50, which emits a signal when the signal emitted by the gratin 45 has a value of zero. Inverter SO output is connected to an input terminal of an AND gate 48, which is simultaneously supplied to a second input with a signal representing tiv for the angular position of the motor shaft. This signal is obtained with it in fig. 3 shows the circuit arrangement.

The signal emitted by the AND gate 48 is then processed as shown in Fig. 4.

Claims (2)

n 'i 447 750 gatentkrav A method of automatically controlling the ignition moment of an internal combustion engine controlled to the optimum operating condition value corresponding in particular to the maximum power and maximum efficiency of the engine, wherein the method of modifying the pressure to occur at a maximum of the motor shaft, characterized by the combination of the following sub-steps: at least one reference angular position of the motor shaft is detected, which position makes it possible to determine the angular positions of the motor shaft; the accelerations to which the cylinder heads of the engine are exposed are detected, and during at least a part of the motor shaft rotation a first signal is generated representing these accelerations; - said first signal is integrated once by an integrator (46) to obtain a second signal, the zero value of which is determined with respect to the angular position of the motor; and - the control of the ignition moment is modified as a function of the angular position assumed by the motor shaft when said second signal has the value zero - Device for automatically controlling the ignition moment of an internal combustion engine, for carrying out the method according to claim 1, which device comprises ignition control means (2) and a detector (20) for detecting the angular rotation of the motor shaft, characterized in that the device further comprises, the part on the engine cylinder cover fixedly mounted accelerometer (18), which generates a first signal representative of the accelerations to which the cylinder cover is subjected; secondly, an integrator (46) connected to the accelerometer (18) which generates a second signal; means connected to the integrator, arranged to receive only said second signal for detecting its zero value during at least a part of the motor shaft rotation; secondly, means (26) connected to said detecting means and the rotation detector, which determine the angular position of the motor shaft corresponding to zero value of the second signal; secondly, comparing means (27) connected to the latter determining means for detecting the deviation between said angular position and a reference position; and said adjusting or adjusting means connected to said comparator means for modifying the ignition control means as a function of said deviation.