FR2701515A1 - Injection control method for multi-point spark ignition engine - Google Patents

Abstract

The invention relates to a method for controlling the injectors of an engine with spark ignition and multi-point injection, four cylinders and four stroke, according to which the injectors are grouped in pairs, the opening of the injectors of each pair is controlled. times per engine cycle, and so that the sequencing of the control of the two pairs is insensitive to the phasing of the engine, and, by adopting the indexing of the engine cylinders for the injectors, the injectors 1 and 4 are paired on the one hand and the injectors 2 and 3 on the other hand, each of the two pairs of injectors 1-4 and 2-3 is controlled during one respectively of two successive engine half-turns, and these two commands are followed by two successive engine half-turns without injector control, then the sequence is resumed as long as the engine is controlled in synchronous operation. Application to the equipment of automobile engines with multipoint injection.

Description

INJECTION CONTROL METHOD FOR ENGINE A

  MULTIPOINT INJECTION WITH COMMAND IGNITION

  The invention relates to an injection control method

  for a spark ignition internal combustion engine equipped with a fuel injection

  fuel injection by indirect injection of the so-called "multi-

  points ", that is to say comprising an injector per cylinder of the engine, and in particular for a four-cylinder engine

  cylinders operating in a so-called "four-stroke" cycle.

  In order to control the injection into such engines, it is known to use a "sequential" method and system, implementing not only an injector per cylinder but also a power stage per cylinder, which determines, in a known manner to from the measurement of different operating parameters of the motor, the duration

  injection, to calculate the amount of fuel

  to inject, as well as the moment of injection or phase

  injection compared to the engine cycle.

  The system comprises means for detecting the High Dead Point (TDC) as well as the angular position of the engine during each engine revolution. These means comprise, in the usual way, a toothed wheel that is rotatably connected to the crankshaft or the flywheel. of the engine, and bearing a target, for example defined by the space corresponding to two missing consecutive teeth, and a sensor integral with the motor and sensitive to the movement of the teeth and the target to deliver signals testifying to the passage of the pistons by the PMH two indexed cylinders, which are generally cylinders 1 and 4 on an in-line four-cylinder engine whose index cylinder 1 is generally the closest to the flywheel, when the target passes next to the sensor, and the rotation of the motor by an angle of 6 when two successive teeth of the wheel pass

of the sensor.

  As the crankshaft performs two revolutions for a complete engine cycle, these means of detecting the rotation of the crankshaft do not discriminate whether, for a given cylinder, the passage through the TDC is the one that starts an admission time or This is why the sequential systems also comprise means for detecting the motor phase, comprising a sensor and a gear wheel with a target similar to those mentioned above, but whose gear wheel is integral in rotation with the gear shaft. cams, which performs a rotation turn through

engine cycle.

  Sequential injection systems, which have a high performance potential because they allow to individualize cylinder by cylinder the amount of fuel injected and the injection phase relative to the engine cycle, have the disadvantage of being expensive, because they require four power stages, a crankshaft rotation sensor as well as a sensor

motor phase.

  To control the injection into such engines, it is also known to use a so-called "full group" method and system, which do not offer the significant performance potential of sequential systems, but allow a substantial gain in cost of the system. system In fact, the "Full group" injection systems have only one electrical power stage and do not include a motor phase sensor. The injection is controlled simultaneously on the four injectors, which are connected in parallel to one another.

  same output of the single power stage.

  A disadvantage attached to a single simultaneous injection by engine cycle is that a cylinder is fed in the compression phase, as a function of the value of operating parameters of the engine, the acquisition of which was made at the end of the preceding engine half-turn. , for an intake phase of this cylinder that will intervene only at the fourth posterior half-turn, while fueling needs, in real time, recalculated and updated each half-turn, have been able to evolve significantly , during transient phases of engine operation. To obtain a relatively regular operation with good transient flow monitoring, the "Full group" systems are generally controlled so that their

  injectors are controlled each turn of the engine, that is,

  ie two times per engine cycle, therefore at a frequency double that of the sequential systems During the first lap, one injects half of the calculated quantity, and during the second lap of the motor cycle, the other half is injected , possibly updated according to the value, between acquired time, of the parameters considered of

engine operation.

  However, this measurement is not satisfactory: the last available acquisition of the parameters used to calculate the injection time and duration is not taken into account. Even if extrapolations are made from the calculated values for the last two acquired measurements of the parameters considered, one can not obtain a

  adapted to the high transient phases of operation

  Moreover, and above all, this dual-frequency control mode of the "Full group" systems is critical with respect to the dynamic response in flow rate of

injectors.

  Indeed, the electromechanical injectors have a flow dynamics which is limited by the ratio between the free or maximum flow, corresponding to an injection

  continue for the duration of the engine cycle, that is,

  say to a permanently open injector (which maximum flow rate is taken into account to size the injector), and the minimum flow (corresponding to a reduction in the opening time, for example at engine idling), the flow rate corresponding to the product of the control frequency by the minimum injectable quantity, which is determined by the control time below which the characteristic of the flow law is no longer linear (order of magnitude of 1 ms, to take account of the establishment current in the coil of the solenoid and the inertia of the moving parts of the injector). "Full group" systems, much cheaper than

  sequential systems, therefore have the disadvantage of presenting

  a much lower flow dynamic than that of

sequential systems.

  In order to find a dynamics of flow equal to that of the sequential systems, or getting closer, for a

  intermediate system cost between those of the sequential

  and "Full group" systems, it has already been proposed a so-called "semi-sequential" injection control method, consisting of grouping the injectors in pairs, each pair of injectors being controlled only once. by motor cycle, that is to say every two motor revolutions, and so that the sequencing of the ordered pairs does not take into account the engine cycle, that is to say does not require information of a motor phase sensor, which can be

to save.

  To implement such a method, a semi-sequential system comprises a position detector

  angle of the crankshaft on each engine revolution, allow-

  in particular to detect the low dead points and low dead points (PMB) of the engine, four injectors grouped into two pairs of injectors, and two stages of electrical power, each of which controls a respective pair of injectors once per engine cycle, that is to say once both

engine laps.

  By indexing each injector in the same way as the

  motor cylinder that it feeds, it has been proposed to

  injectors 1 and 2 in one pair and injectors 3 and 4 in the other pair, injectors 1 and 3 in one pair and injectors 2 and 4 in the other pair, and finally injectors 1 and 4 in one pair and the injectors 2 and 3 in the other pair Similarly, it has been proposed to carry out the sequencing of the control of the two pairs of injectors in several ways, provided that the

  control period is two engine revolutions.

  But, in all cases, it has been proposed to control the two pairs of injectors symmetrically or regularly over the period of two engine revolutions, that is to say to order two injections equi-distributed over the period, and for each of which the two injectors of the pair

  corresponding data are simultaneously controlled.

  Each of the two injections is ordered during one of

  two half-turns separated by a half-turn without injection.

  In Figure 1, there is shown a schematic diagram for each of the four cylinders cyl 1 to cyl

  4 of the engine, shown in superimposed lines, the success-

  during the course of nine successive half-turns (in adjacent columns) of the four successive phases of admission, compression, expansion and exhaust which constitute a motor cycle, the intake phases being indicated by dotted lines 1, for a motor whose four injectors are matched according to the third choice presented above (injectors 1 and 4 in one pair, injectors 2 and 3 in the other pair) with regular distribution of the injection controls, marked by elongated solid rectangles 2, and assuming that the first half-turn corresponds to an intake phase for the cylinder 1 If the delay or response time is called the delay, represented by a continuous solid line 3, between the instant A of the last acquisition values of the parameters used to calculate the quantity A injected and the actual admission for the cylinder in question, it is found that this delay is small for the cylinder 1, greater than half a turn for the e cylinder 2, greater than three half-turns for the cylinder 3 and greater than two half-turns for the cylinder 4 Let a sum of

  delays greater than six half-turns for the four cylinders

  dres, so an average delay of 1.5 half-turn.

  If the admission to the first half-turn is at cylinder 4 and not at cylinder 1, there are delays greater than two half-turns for cylinder 1, at three half-turns for cylinder 2, at half a turn for the cylinder 3 and weak

  for cylinder 4, the same total and the same average.

  It is the same if we change the sequencing of the ordered pairs, that is to say if, at the first half-turn, we

  controls the injection into the cylinders 2 and 3, and the third

  second half-turn in cylinders 1 and 4, that the admission

  at the first half turn, either to cylinder 1 or cylinder 4.

  The insensitivity of this pairing of the injectors to the engine phasing is well obtained in terms of the sum and average of the delays, and we note that the other two

  possible pairing configurations are less

  in terms of sensitivity to motor phasing or time

delay.

  The search for a good regularity of functioning

  This naturally leads to a preference for the pairing of injectors 1-4 and 2-3. However, the response time or delay remains too important for two cylinders.

out of four.

  The problem underlying the invention is that of

  short response times, in order to make such a semi-sequential control system less sensitive to

  phases of transient operation of the engine.

  An object of the invention is to reduce both the maximum value of the response time and its average value.

  in such a semi-sequential control system.

  Another object of the invention is to allow the removal of exceptional, asynchronous injections, which

  may possibly be added during the course of

  of a "full group" or even semisequential control system, which would be allowed to compensate

  insufficient power supply in the event of accelerated

important, for example.

  Another object of the invention is finally to choose a pairing of the injectors as well as a sequencing in the control of the pairs of injectors which guarantee an operation of the system insensitive to uncertainty.

relating to the engine phase.

  For this purpose, the invention proposes a method for controlling the injection of an internal combustion engine, with a spark ignition and multipoint injection, with four cylinders and operating in a four-stroke cycle, which comprises an injector per cylinder, the method comprising the steps of grouping the injectors in pairs, controlling the opening of the injectors of each pair only once per engine cycle, and so that the sequencing of the control of the two pairs of injector is insensitive to the phasing of the engine , and which is characterized in that it further comprises the steps of, if indexing each injector with the same index as the cylinder of said engine that it feeds, to match the injectors 1 and 4

  on the one hand and injectors 2 and 3 on the other hand,

  der each of the two pairs of injectors 1-4 and 2-3 during one respectively of two successive engine half-turns, and to follow these two commands of two successive engine revolutions without control of injectors, then resume the sequence, as long as the engine is driven in

synchronous operation.

  It can be seen that the choice of the pairing of injection

  Both the motors and the choice to control the two pairs of injectors each during one or two successive motor half-turns, have the advantages of making the operation insensitive to the uncertainty of the phase.

  engine, and to minimize the delay time between acquiring

  the parameters used to calculate the injection time

  tion and actual fuel injection into the engine cylinders, which provides better

of the latter in transitory.

  These advantages are obtained both with a control sequencing of first controlling the pair of injectors 1-4, then the pair 2-3, that the cylinder 1 or the cylinder 4 is in the admission phase during the half-turn control motor of the pair 1-4, that with the control sequence consisting first to control the pair of injectors 2-3, then the pair 1-4, and that the cylinder 2 or the cylinder 3 in the intake phase during the engine half-turn during which the injection is

  ordered for cylinders 2 and 3.

  Advantageously moreover, the injection control method according to the invention comprises the step of determining the sequencing of the control of the two pairs

  injectors (pair 1-4 then pair 2-3, followed by two half

  engine revolutions without control, then again from the control of the pair 1-4 then of the pair 2-3, or command of the pair 2-3 then of the pair 1-4, followed by two half-turns motor without control , then again the control of the pair 2-3 followed by the pair 1-4) depending on the situation of the engine with respect to its cycle, at the moment of entry into synchronous operation phase of the engine, for example following a start of the engine or on the occasion of a

  resumption of injection after a cut of the latter.

  According to an advantageous embodiment, the method

  in accordance with the invention consists in choosing the sequence

  control of the pair of injectors 1-4 and then of the pair 2-3, or the control sequencing of the pair of injectors 2-3 and then of the pair 1-4, according as the first signal of Dead Point High (PMH) or Low Dead Point (PMB) given by a motor rotation sensor after motor input in synchronous operation phase is a signal of

PMH or PMB respectively.

  In addition, the method may consist, in addition, of introducing a delay between the determination of the sequencing of the control of the pairs of injectors, for example as a function of the first PMH or PMB signal, and

  the actual course of the injection as a function of

  previous regulations, such as starting the engine or

  injection cutoff, for example deceleration.

  Other advantages and features of the invention

  will flow from the description given below,

  nonlimiting title, embodiments described with reference to the accompanying drawings in which: Figure 1, already presented and described above, corresponds to a diagram schematically the different phases of the engine cycle for each of the four cylinders, with indication of intake phases, injection controls and response times for a so-called semi-sequential system with injector or cylinder 1-4 and 2-3 coupling, and regular injection control, symmetrical or equi-distributed 2 is a diagram similar to that of FIG. 1 for a semi-sequential system which is also coupled to cylinders or injectors of index 1-4 in the first pair and of index 2-3 in the first pair. second pair, but with asymmetric injector control, specific to the invention, and

  FIG. 3 represents two possible sequencing

  control of the pairs of injectors, which are chosen as a function of the first PMH or PMB signal detected during the input of the motor during the synchronous operation phase, either after starting or during a restart

  injection, following a cut of it.

  It will be recalled that the consequence of a symmetrical injector-controlled semi-sequential operation, as described above with reference to FIG. 1, leads to maximum response times greater than three motor half-turns, to a sum response times greater than six engine half-revolutions, and therefore an average of response times of the order of 1.5 half-turn engine per cylinder, the other possible variants of semi-sequential operation

  controlled by symmetrical injectors presenting

  in terms of time delays and in terms of sensitivity

  to the uncertainty of engine phasing.

  In FIG. 2, the intake phases are also represented by the reference 1, the injector controls by the reference 2 and the response times by the reference 3, under the same conditions as in FIG. 1. it is found that the pair of injectors 1-4 is controlled during the first half-turn, for which the cylinder 1 is in the intake phase, and that the pair of injectors 2-3 is controlled during the half-cycle. immediately following engine revolution, that is to say the second motor half-turn, for which the cylinder 3 is in the intake phase None

  Injector control does not occur during the two half

  subsequent engine revolutions, for which the cylinder 4 and then the cylinder 2 are successively in the intake phase At the first half-turn of the next engine cycle (the fifth half-turn in FIG. 2), the injectors of the pair are again controlled 1-4, then, at half-turn motor immediately following, it again controls the pair of injectors 2 and 3, after which two engine half-turns follow one another without control of injectors This gives the sequencing shown in the first line of FIG. 3, which is kept as long as the motor is controlled in synchronous operation. This sequencing follows the detection, at the beginning of the first half-turn, of a TDC for the inlet cylinder 1, but, alternatively, could be

  that of the intake cylinder 4 The engine cycle begins-

  then from the third engine half-turn of the

figure 2.

  In this FIG. 2, the last acquisitions A of measured values of the operating parameters of the engine used to calculate the quantity of fuel to be injected, and which precede the injector controls, are those obtained respectively at the beginning of each of the first two It is thus noted that for the cylinders 1 and 3, the delay time is low, whereas it is slightly greater than two engine half-revolutions for the cylinders 2 and 4. The maximum value of the delay times is thus decreased, compared to a control according to Figure 1, the sum of the delay times being more than the order of four half-turns motor, which corresponds to an average

  about half a motor revolution per cylinder.

  The maximum response time, the sum of the response times and their average are thus well reduced. These advantageous results are also obtained if the control sequence of the pairs of injectors shown in FIG.

  second line of Figure 3, namely a first

  request of the pair of injectors 2-3, followed by a command,

  immediately following motor turn-around, of the pair of in-

  jets 1-4, then two half-turns motor without control, then again the control of the pair of injectors 2-3 followed by the control of the pair 1-4, etc., as long as the

  motor remains controlled in synchronous operation.

  Such a sequencing can begin with the control of the pair 2-3, after passing through a PMB, for example during the second half-turn of FIG. 2, for which the cylinder 3 is in the admission phase, or during the fourth motor half-turn of Figure 2, for which the cylinder 2 and in the intake phase. FIG. 3 and FIG. 2 show that, when the motor enters the synchronous operating phase, either after it has been started or during a resumption of injection, following an injection cut due to a deceleration for example, the sequencing automatically adopted by the central control unit of the device, comprising a microprocessor suitably programmed for this purpose, will be that of the first line of Figure 3 if the first signal of PMH or PMB detected by the engine rotation sensor is a PMH signal, and will be sequencing the second line of Figure 3 if

  this first detected signal is a PMB signal.

  We understand that the device to put

  the process according to the invention can be rigorous-

  identical to a symmetrically controlled semi-sequential device, but that the microprocessor of the control unit will be programmed differently to ensure the asymmetric injector controls according to the sequencings described above. Of course, the engine rotation sensor is the same as in the known devices, namely a gearwheel sensor with a singularity for the detection of the PMH, this toothed wheel being integral in

  rotation of the crankshaft or flywheel.

  To avoid engine operation jolts, which may for example result from an injection resumption too

  following a deceleration cut, a temporisa-

  possibly adjustable, can be introduced between the determination of the control sequence to be adopted following the detection of a PMH or a PMB, and the recovery

effective injection.

  It is generally accepted that the control of the injection of fuel into a cylinder in the intake phase is very unfavorable to a good preparation of the fuel-air mixture. From this point of view, the control method according to the invention can be considered as disadvantageous, insofar as it goes against this teaching, since FIG. 2 shows that the opening of the injectors of the cylinders 1 and 3 is controlled while the latter are in the intake phase But the advantages of the process of the invention, namely the best behavior of the

  transient motor, far outweigh the inconvenience-

  mentioned above, which can be easily compensated by the

  exhaust gas treatment in a catalytic converter

  under good temperature conditions, in accordance with

  the latest anti-pollution standards.

Claims (4)

  A method for injection control of a four-cylinder, four-stroke, four-stroke, multi-point, positive-ignition engine and comprising an injector per cylinder, the method comprising the steps of grouping the injectors in pairs, controlling the opening of the injectors of each pair only once per engine cycle, and so that the sequencing of the control of the two pairs is insensitive to the phasing of the engine, characterized in that it further comprises the steps consistent, if we index each injector   with the same index as the cylinder of the engine   to match the injectors 1 and 4 on the one hand and the injectors 2 and 3 on the other hand, to control each of the two   pairs of injectors 1-4 and 2-3 during a respective   two successive engine half-turns, and to make these two commands follow two successive engine half-turns without injectors control, then to resume the sequence as long as   the motor is controlled in synchronous operation.   2 injection control method according to the   cation 1, characterized in that it further comprises the step of determining the sequencing of the control of the two pairs of injector (1-4 and 2-3, or 2-3 and 1-4) depending on the situation of the engine with respect to its cycle at the moment of entry into synchronous operation phase of the engine, for example following a start of the engine or during a resumption of injection after cutting the latter.   3 injection control method according to the   cation 2, characterized in that it consists in choosing the control sequencing of the pair of injectors 1-4 and the pair 2-3 or the control sequencing of the pair of injectors 2-3 and the pair 14, depending on whether the first PMH or PMB signal given by a motor rotation sensor after the motor input during operation   synchronous is a signal of PMH or PMB respectively.   4 Injection control method according to one   any of claims 2 and 3, characterized in that   that it consists, moreover, in introducing a delay between the determination of the sequencing of the control of the pairs of injectors 1-4 and 2-3, and the actual course of the injection as a function of previous events, such as engine start or injection cut, by example in deceleration.