FR2477231A1 - INSTALLATION FOR GENERATING A FUEL DOSING SIGNAL FOR AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

A. THE INVENTION RELATES TO AN INSTALLATION FOR PRODUCING A FUEL DOSING SIGNAL FOR AN INTERNAL COMBUSTION ENGINE, INCLUDING A ROTATION SPEED MEASURING APPARATUS 10, A MASS COUNTER OF NONLINEAR AIR 11, AS WELL AS A PRODUCER STAGE OF DOSING SIGNALS CONTAINING AN ACCUMULATOR 12 AND AT LEAST ONE INJECTION VALVE 13. B. THIS INSTALLATION IS CHARACTERIZED IN THAT BETWEEN THE MASSIC AIR METER 11 AND THE ACCUMULATOR 12 IS CONNECTED TO THE D SERIES ASSEMBLY 'A CORRECTING ORGAN 14A AND A SUMMING ORGAN 15A. C. THE INVENTION IS APPLICABLE TO THE FUEL SUPPLY OF INTERNAL COMBUSTION ENGINES.

Description

1.- The invention relates to an installation for producing a signal of

  fuel metering for an internal combustion engine, comprising a non-linear mass air counter and a

  stage producing a dosing signal containing an accumulator member.

  In a fuel metering system, the most important quantities to be dealt with are the rotational speed and the load condition. To determine the load, we use

  pressure sensors or air mass counters.

  with a retaining flap. Recently, mass meters

  heated wire have proved particularly advantageous because

  that they have no moving mechanical element and furthermore because they can take into account the temperature of the intake air

in the measurement result.

  In order to be able to dose a desired mixture as accurately as possible, it is necessary to determine the air mass sucked during an operating time of the internal combustion engine. However, existing air mass meters measure only the airflow, ie the mass of air per unit of time, so that the air mass desired for an admission time must be determined indirectly by an integration of the airflow in function

time.

  The flow rate or mass of air flowing per unit of time is not constant during a running time but has a

  wavy pace as a function of time due to the opening movements

  different closing and closing of the various intake valves

  that resonance phenomena occurring in the intake manifold

  if we. In the case of a linear air mass measuring device, in

  which the electrical output signal of the measuring member is proportionally

  In the air flow rate, this wavy pace as a function of time does not cause difficulties because the integral of the electrical signal is also proportional to the integral of the air flow (= air mass). For this reason, this integral can be used directly to

  the control of the time member of an injection installation.

  However, the proportionality between the integral of the air flow and the electrical signal is generally no longer satisfied for a non-linear mass air counter, for example for a heating wire air mass counter. Problems then arise insofar as this defect of proportionality can not be corrected by a field of characteristics stored in memory because the integral of the electric signal f, which is in turn a function of the airflow g, 2 that is to say the time t and the specific operating conditions Xi of the motor (X1 = load, X2 = rotation speed, etc.) is not a single function of the operating conditions Xi. It can not therefore be used to characterize the state of the engine at the instant considered and to determine the quantity of fuel to be determined I (X X2 -..., X) = Jf [g (X1, X21 ... Thus, the invention poses the problem of transforming, with simple means, the transmission or transfer function f (g) of the mass counter of a single function (X1, X2, ..., Xi). air, so that the integral I of the electrical measurement signal f thus modified becomes a univocal function of the specific operating conditions of the motor (speed of rotation, load). The value of the integral then determines, through a field of characteristics, the quantity of fuel

to be dosed.

  The unambiguous nature of the value I of the integral is obviously guaranteed when, as is the case for the currently known fuel metering systems, the air mass measurement signal is made linear in a fast-moving manner. as much as possible from the ideal, so that there is an exact proportionality between the air flow and the linear electrical signal; US Pat. No. 4,043,196 discloses an arrangement for providing maximum linear correction. In this assembly, a function generator is connected to a meter

  mass of air heating wire, this generator can produce the function

  (Y / Z) n with definite Z and n values.

  In view of the mass production of

  fuel metering equipment, the use of correct assemblies

  Linear factors have proved to be too complex and therefore too expensive. The problem also arises of the accuracy of the linear correction and, in this respect, also the question of the possible interchangeability of individual groups, without having to take any

important calibration measures.

  In view of the problem raised, the object of the invention is to modify the transfer characteristic of the air mass counter simply so that the unambiguous nature of the value of the integral remains guaranteed. It is therefore enough to make the value of the electrical signal of the air mass counter substantially linear (= quasi-linear)

  depending on the air flow in the intake manifold.

  3. To this end, the invention relates to an installation of the above type characterized in that between the mass air counter and the accumulator member with a field of characteristics is connected the series connection of a corrector unit. such as a prior correction or linear correction circuit and a summing element such as

integrator or counter.

  To achieve this quasi-linear correction,

  simple electronic assemblies can be used and * thus economically

  provided that the integrated electrical signal I is used to determine the quantity of fuel to be

  passage through a field of characteristics.

  The invention will be better understood with regard to the

  description below and accompanying drawings showing two examples

  Embodiments of the invention, in which: Fig. 1a and Fig. 1b are block schematic diagrams of the electric part of injection facilities; Fig. 2 is a diagram showing the characteristic of a air mass meter with heating wire, - Figure 3 shows the variation according to

  from the time of the air flow passing to the air mass meter and the vari-

  corresponding, non-proportional, as a function of time of the output voltage of the air mass counter and the corresponding integration surfaces,

  - Figures ha to 4c are graphs intended

  25. born to explain the transmission behavior during a quasi-linear correction corresponding to the assembly of Figure la, - Figures 5a to 5c represent the adaptation

  of the transfer characteristic of the quasi-correction

  linear circuit according to FIG. 1b (here a non-linear voltage-frequency converter) to the characteristic of the heating wire air mass counter; FIG. 6 represents a first embodiment of a non-linear voltage-frequency converter, FIG. represents a second example of

  realization of such a converter.

  The following description is for examples

  relating to fuel injection facilities. The invention, however, does not concern the injection installation as such, but firstly the preparation and treatment of the value of a

  signal in analogue form. For this reason, the invention

  4.- tion can also be implemented, for example in the context of controlled carburettor installations or diesel injection facilities. FIGS. 1a and 1b are block assembly diagrams of the electrical part of injection installations. A rotational speed measuring apparatus and a mass air counter are designated. The two outputs of these devices are connected directly or indirectly to a time member or accumulator member 12 to form injection pulses t intended for an injection valve 13. Between the mass air counter 11 and the organ 12 is a series circuit comprising either a quasi-linear correction circuit 14a and an integrator 15a, or a non-linear voltage-frequency converter 14b (approximately linearly correcting the non-linear characteristic of the heating wire) and a counter. L4B. The integration limits of the integrator 15a as well as the counting limits of the counter 15b are determined by

  signals from the rotational speed measuring device 10.

  With the assemblies shown in FIGS. 1a and 1b, in the integrator 15a or in the counter 15b, a quantity can be uniquely associated with the air mass.

  flowing in the intake manifold at each operating time.

  From the final value in the integrator or in the counter and the output signal of the rotational speed measuring device, an appropriate injection value, for example

  in a three-dimensional feature field contained in the

  The link line drawn in broken lines between the time member or accumulator member 12 and the injection valve-13 is intended to indicate that it is still possible to provide in this line.

  correction stages, for example for accelerating enrichment

tion.

  Figure 2 shows the characteristic of a heating wire air flow meter. In the diagram, the output signal of the heating wire airflow meter is plotted against the mass of air per unit of time flowing in the air intake manifold. The ideal case would be to have an initial right with an ascending slope. For various reasons, however, this ideal case can not be obtained, but there is essentially a parabolic branch starting from a voltage value of the heating wire different from zero for a flow rate.

mass of air equal to zero.

  Figure 3 represents the problem that arises.

  for the correct determination of the air mass in the case of a

  nonlinear mass masseur. In the first quadrant of the coordinate system, the characteristic of the heating wire was drawn. In the second quadrant (turning to the right), the variations of the effective air mass are shown whose representative curve has a wavy shape due to the different opening and closing movements

  various intake valves. The tension of the heating wire represents

  in the fourth quadrant corresponds to a transposition of the air mass according to the characteristic represented in the first quadrant. The shape of the curve is distorted compared to that of the second quadrant. It has been indicated by hatching the integral in function

  time for the second quadrant and fourth quadrant curves.

  For the digital signal processing, it has been judicious to postpone each airflow on a time grid and to sum the corresponding values after having multiplied by a time interval. The error is visible in this case

  also due to the lack of linear deviation of the heating wire.

  Due to the lack of linearity of the heating wire air mass counter, dual values for each integrated value can be given, so that errors can occur during the subsequent processing of the signals. The task of avoiding this is fulfilled by the quasi-linear correction effected by means of the quasi-linear correction arrangement I4a according to FIG. 1a or by means of the non-linear voltage-frequency converter 14a of the arrangement according to FIG. The degree of linear correction then depends on the probability of appearance of double meanings in the output signal of the integrator. This is highlighted by referring to the diagrams

  Figures ha to 4c and 5a to 5c. Figures 4a to 4c show the adaptation

  the transfer characteristic of the quasilinear correction arrangement according to FIG.

  mass of air heating wire. Figures 5a to 5c show the adaptation

  tation of the transfer characteristic of the quasi-correction

  Linear in the form of a nonlinear voltage-frequency converter corresponding to the assembly of Figure lb to the characteristic of the heating wire air mass counter. In FIG. 4a as well as in FIG. 4b, the output signal of the heating wire air mass counter is plotted as a function of the flow rate or quantity of air per unit.

  of time flowing into the intake manifold. Figure 4b shows

  the characteristic of the quasi-linear correction arrangement I4a of the object of FIG. 1a, so that the output voltage, shown in FIG. 4c, of the quasi-linear correction arrangement 14a is reported.

depending on the air flow.

  Similarly, it was reported according to the

  airflow, in FIG. 5b the transfer behavior of the converters

  non-linear voltage-frequency converter 14b of the object of FIG.

  in FIG. 5c, the output signal of this converter 14b.

  No example of the realization of the

  quasi-linear correction stage 14a because the function generators for similar signal levels are generally known and can be realized, for example, by means of diode and resistor networks. The sizing must be carried out in any case according to the mass meter of air used and can not be

given here in a lump sum manner.

  Figures 6 and 7 show two examples of

  realization of non-linear voltage-frequency converter.

  The main parts of the voltage-to-voltage converter

  The frequency shown in FIG. 6 is a capacitor 20, a comparator stage 21 and a D flip-flop 22. From an input terminal

  23, a resistor 24 is connected to the negative input of the comparator stage.

  21 and a terminal of the capacitor 20 which is further connected to ground. The positive input of the comparator stage 21 is connected to ground via the parallel connection of a capacitor 25 and a resistor 26. This input is further connected, via a resistor 27, to a reference voltage source not specifically designated. On the output side, the comparator stage 21 is connected to a positive conductor 29 via a resistor 28 and simultaneously provides the input signal for the D flip-flop 22. While the output Q of this flip-flop 22 is coupled with an output terminal 30 of the voltage-frequency converter, the signal of the output Q controls an inverter 31 through which the two-point signals

  connection 33 and 34 can be sent to the capacitor 20 via

  The connection point 33 is connected to the connection point of two resistors 36 and 37 together forming a voltage divider between the point of connection 35. the input terminal 23 and the ground. An essential point of the object of FIG. 6 is the charging and discharging of the capacitor 20 according to

  of the output signal of the flip-flop D 22 by means of two sources of

  (35 and 36, 37) independent of the rest of the 7.electric power supply, the non-linearity of the voltage-frequency converter being

  obtained by the non-constant voltage value at the input 34.

  The operating mode of the voltage-to-voltage converter

  The frequency shown in Fig. 6 is such that the comparator latch switch-on 21 each time results in a potential change at the output terminal 30 of the converter. Due to the charge and discharge of the capacitor 20 controlled by the output signal, the frequency of the output signal is in definite relationship with the

analog input signal.

  With the object of Figure 6, there is a relationship

  determined between the change of the output potential of the comparable stage.

  21, the clock frequency controlling the flip-flop D 22, as well as the instant of switching of the inverter 31. This determined relationship does not prove very beneficial when a constant relationship between the input signal and the signal is desired. output signal. In this case, it has proved advisable to complete the flip-flop D 22 of FIG. 6 to obtain a monostable flip-flop with a quantization time base.

  digital. A corresponding example is shown in FIG. 7.

  Figure 7 is based on the construction of Figure 6, the D flip-flop 22 shown in Figure 6 is, however, replaced by the series connection of a synchronization stage 40 and a flip-flop monostable 41 digital operation. The synchronization stage 40 comprises two inverters (Schmitt triggers) 42 and 43 connected one after the other and arranged in the line going from the output of the comparator stage 21 to an input D of a D flip-flop 44 of the synchronization stage 40. On the output side, this flip-flop D is connected to the whole of the monostable flip-flop stage with the series connection of a bistable flip-flop stage 45, a flip-flop D 46, a counter 47 and a decoder device 48. The two outputs of the bistable flip-flop stage 45 are combined with the following D flip-flop 46 as well as with the control input of the inverter 31. The output Q of the flip-flop D 46 is connected to the return input of the counter 47. The decoder device 48 essentially consists of a NAND gate 49 whose output is connected to the second input of the bistable flip-flop stage 45. one of the inputs of this NAND gate 49 is still combined with the first input of the bistable flip-flop stage 45 to which is also applied the output signal of the synchronization stage 40. As a result, the decoder device

  48 sends a return pulse to the second input of the floating stage.

  Bistable lant 45 only if, beforehand, the comparator stage 21 and the stage 8.- synchronization. 40 were switched. At exit 30 is finally connected

  a conductor 50 from the MSB terminal of the counter 57.

  In the object of FIG. 7, an essential element is constituted by the monostable flip-flop realized by means of the counter and the decoder device, this flip-flop thus being able to provide a numeric quantization pause time corresponding to the frequency of cadence. With this monostable tilt stage, a pulse duration can be set, while the duration of the period of the output signal at the output 30 is a function of the signal at the terminal

23.

  The two voltage-frequency converters described above have proved extremely judicious in connection with the assembly shown in FIG. Due to the correction

  only partial linearity of the air mass signal and the correction of

  residual reaction carried out in the time organ 12 via

  characteristics field, it is not necessary that the characteristic

  The transfer risk corresponds in principle to a precise mathematical function. It suffices that it is of strictly reproducible nature, which has proved advantageous in the interest of mass production.

extremely economical.

9.-

Claims (7)

  1.- Installation for producing a fuel metering signal for an internal combustion engine, comprising a nonlinear mass air counter (11) and a metering signal producing stage containing an accumulator member (12), installation characterized in that between the mass air counter (11) and the accumulator member (12) with a field of characteristics is connected the series connection of a correction element such as a correction circuit or a linear correction circuit (14a). , 14b) and a summing organ   integrator (15a) or counter (15b).   2. Installation according to claim 1, characterized in that the degree of linear correction depends on the probability or the existence of double meanings appearing in the output signal of the integrator (15a) or in the counting level. final counter (15b) in the case of a non-linear input signal. 3. Installation according to claim 1, characterized in that the linear correction arrangement is arranged   in the form of a non-linear voltage-frequency converter (14b).   4.- Installation according to any of the   Claims I to 3, characterized in that the mass air counter   (11) comprises a heating wire and / or a heating film.   5. Installation according to claim 3, characterized in that the voltage-frequency converter (14b) comprises   the series connection of an accumulator member (20), a comparator stage   (21) and a tilting stage (22, 41), the output signal of the tilting stage connects the storage device to the sources of charge and discharge.   6.- Installation according to claim 5, characterized in that the rocking stage (41) is constituted by a monostable rocking stage with a time base quantifiable by means of a   counting and decoding circuit.   7.- Installation according to claim 5, characterized in that the discharge signal of the accumulator member   (20) depends on the input signal of the voltage-frequency converter (14b).