JPS6044504B2 - Method and apparatus for controlling the mass ratio distribution of a fuel-air mixture supplied to an internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses an oxygen detector (λ detector) placed in the exhaust gas stream to control the mass ratio distribution of the fuel-air mixture supplied to an internal combustion engine (λ detector). A method and apparatus comprising: integrating the output voltage of the oxygen detector at least indirectly to produce an output adjustment voltage that controls the composition of the fuel-air mixture; The present invention relates to a method and apparatus of the type in which the stoichiometric ratio of air is asymmetrically shifted to the lean or rich side.

It is known to control the mass ratio of the fuel-air mixture supplied to an internal combustion engine, i.e. the excess air ratio λ, as a function of the composition of the exhaust gas, in which case oxygen detectors or A λ detector is arranged which, depending on the composition of the exhaust gas, can generate an output voltage whose waveform and switch operation will be explained later. This output voltage of the λ detector is fed to a regulating device, which regulating device is advantageously designed as an integral regulator;
And instantaneous internal combustion engine depending on the output voltage! Appropriately increase or decrease the amount of fuel allocated to Such a change in the excess air ratio λ of the fuel-air mixture can be carried out both in an internal combustion engine with a carburetor and in a fuel injection device, which normally changes the amount of fuel supplied to the internal combustion engine. can be adjusted more precisely over the operating range of this internal combustion engine. Therefore, in such a system, the internal combustion engine itself exhibits a regulating section, resulting in a dead time for the regulating system, which is defined below as engine dead time or engine transit time 4Tt. do. This dead time varies during driving, primarily depending on the rotational speed of the internal combustion engine. When adjusting using the output voltage of an oxygen detector, the characteristic curve of the detector has a special significance, which is shown schematically in FIG. ) can take on two different switch states.

A first switch state corresponds to an output voltage of approximately 9007n,V, for example, and occurs when the oxygen detector in the exhaust pipe detects a rich fuel-air mixture, and another output voltage corresponds to approximately 100Tr1.V. (2) and corresponds to the lean fuel-air mixture originally supplied to the internal combustion engine. The transition between the two detector voltages actually takes place abruptly when the value of the excess air ratio is λ=1. Although in a real implementation there is a finite degree of tolerance, the curved course of the detector characteristic curve at ON = 1 leads to a somewhat denser air excess rate when a correspondingly high voltage threshold is given in advance. It can only be adjusted. Even considering this drawback, it is still a disadvantage to operate with a curved, even less sensitive, portion of the detector characteristic curve. This is because this part is temperature dependent and easily ages. In today's conventional detectors, the almost stable characteristic point of the detector characteristic curve is approximately 300 to 350 m. 1, and corresponds approximately to point P in FIG. On the other hand, if it is actually desired to operate at point P of the detector characteristic curve, a predetermined value of the excess air ratio λ is determined. However, since it is desirable to achieve a variation width of at least approximately ±5% around the air excess ratio λ = 1, the internal combustion engine is adjusted within a freely selectable range between approximately λ = 0.95 and 1.05. can. The object of the invention is to provide an internal combustion engine with a λ adjustment that allows a stable characteristic point of the detector characteristic curve to be selected as a threshold value and still allows for an appropriate variation of the excess air ratio λ. An object of the present invention is to provide a method and apparatus for controlling the mass ratio distribution of a fuel-air mixture.

This object is achieved according to the invention, starting from a method of the type mentioned at the outset, in the following manner.

That is, a single integrator is supplied with a delayed control voltage that is dependent on the detector output voltage, with said integrator continuing to integrate in the direction of ) for a predetermined period after the actual detector switching point. controlling the integrator integration characteristics such that and for the predetermined period of time the integrator is further configured such that a sudden steepening of the integrator output signal occurs in the direction of a new desired adjusted average λ value; Control. For example, the characteristics of the integral regulator can be changed by an arbitrarily adjustable waveform modification of the integral regulator output voltage supplied to the actuator for the fuel metering.
Since it can be controlled to adjust to any average λ on the rich and lean sides when using a λ detector or an oxygen detector, the concept for a diluted λ with a given λ also consumes very little fuel. This can be achieved by air injection without increasing the amount.

When operating an internal combustion engine, it is generally desirable to be able to vary the air quantity in the basic adjustment or even during operation. If necessary, according to the invention, the operating point for the excess air ratio can also be varied as a function of the rotational speed of the internal combustion engine, for example for the integral regulator output voltage as a function of the rotational speed, as explained below. It can also be changed by acting on the regulating element. Embodiments of the present invention will be described below with reference to the drawings.

Before explaining the present invention and its embodiments in detail, the following will be stated. Thus, in fact, the invention is applicable to all systems in which it is possible to carry out an adjustment of a predetermined value of the fuel-air distribution supplied to the internal combustion engine, for example by means of an actuator acting on the output voltage of a regulator. It is. By varying the fuel supply in dependence on the detector voltage by means of a mechanical actuator, for example by means of an electromagnetic control valve, it is clearly possible to vary the settings of various carburetor configurations in this way. However, the invention can particularly advantageously be applied to systems of electronic fuel injection devices, which supply, for example, opening pulses of variable duration to injection valves, which are associated with an internal combustion engine. In addition, it can be constructed so that it can be opened and closed using an electromagnetic method. Through conduits to these injection valves,
The fuel to be injected is supplied at a constant pressure for the purpose, and the duration of the opening pulse determines the amount of fuel that is supplied to the internal combustion engine from stroke to stroke or continuously. In such an electronic fuel injection system, a control device is connected before the output final stage that directly controls the injection valve, and this control device generates an output pulse, and the duration of this output pulse is the final output stage. The duration of the control command supplied to the injector can be determined. The control device can then consist of a monostable multivibrator, which can be activated via a time capacitor in the return path. The instability time of a monostable multivibrator is determined by the charging and discharging of the capacitor, while the charging and discharging time of this capacitor is determined by the action of the discharging and charging sources for this capacitor. The discharge current is a measure of the air excess rate supplied to the internal combustion engine, which air excess rate can be detected and converted in any way, and the charging current is related to the rotational speed of the internal combustion engine and is therefore dependent on the rotational speed. is synchronized with. It is not necessary to go into detail regarding the particular configuration of the electronic components of the internal combustion engine. All that matters is that the fuel injector is configured in such a way that the amount of fuel delivered to the internal combustion engine can be suitably controlled by the varying voltage supplied to the fuel injector. be. Adjustment to a desired excess air ratio λ in the electronic fuel injection device can be performed, for example, as follows.

That is, an oxygen detector is arranged in the exhaust pipe of the internal combustion engine, which oxygen detector supplies a detector voltage Us as a function of the exhaust gas composition, the course of this detector voltage with respect to time being It is indicated by a thick solid line in Figure 1. For simplicity, the effective course of the detector voltage is also shown in dashed lines in the same diagram of FIG. 1, corresponding to curve B;
, which likewise shows the course of the detector characteristics under temperature and aging effects as curve C.
The course of the detector characteristic curve has a steep slope at λ=1 and is curved at λ lamp 1, but in principle all curve courses have in common an approximately stable characteristic point,
Moreover, it can be seen that the curve course of FIG. 1 has a point P, which point P is therefore used as a threshold value in the invention, as explained below. For this purpose, a detector threshold circuit is provided, which will be explained further below. That is, the output voltage of the detector threshold circuit then reaches an integral regulator, which is formed according to the features of the invention to be explained further below, the output terminal of which produces a varying voltage, which A voltage is supplied to the electronic fuel injector to regulate the amount of fuel delivered as described above. Before explaining this in detail, the basic idea of the present invention will be explained with reference to FIGS. 2a and 2b.

During the normal lambda adjustment using an oxygen detector and an integral regulator, the fuel-air mixture just passes through the lambda value 1 at time t1 in FIG.

This λ value can be measured by a detector with a steep characteristic curve. This air-fuel mixture is drawn in by the internal combustion engine and processed and reaches the detector only after an engine transit time Tt, which detects, by changing the indicated voltage at time t1+π, that λ=1 has been reached. Inform. At this point t1
The integral regulator continued to adjust the mixture until +Tt.
From this moment on, the adjustment is made in the opposite direction and at time T2 the value which brings the mixture to λ=1 is reached again. On the other hand, time T2+
Since for the first time at Tt this state of the mixture supplied to the internal combustion engine is detected by the oxygen detector, it is clear that there is a steady state of the fuel-air mixture around the mean value at the excess air ratio λ = 1. Oscillation occurs. In order to be able to adjust the fuel-air mixture to such a λ value, preferably to λ = 0.99, as is necessary for example for embedded catalysts to reduce exhaust gas pollutants, The average input value is moved by changing the characteristics, and the curve shape of the integral regulator output signal is also changed.

A first embodiment that allows for a variant is shown in FIG. 2a, which shows the course of the regulator output voltage UR over time.

At time t1, the air excess ratio of the fuel-air mixture supplied to the internal combustion engine has the value 1, but the λ detector is not yet able to respond to this. This is because the λ detector can detect this value only after the engine transit time Tt has elapsed. At time t1+Tt, the output signal is
According to the feature of the present invention, the integral regulator shown in FIG.
The regulator output signal U is shifted by the value ΔU in the direction in which the value is to be shifted.
It is controlled to shift R rapidly. Then, after performing this sudden change, the regulator integrates in the opposite direction,
And it passes through the zero line at time T2. λ at time T2+Tt
The detector again signals the presence of λ=1, and the regulator output signal shifts upwards again in this example,
This clearly results in a center deviation of the regulator output voltage by the value ΔU/2. This deviation is independent of the value of the engine transit time Tt. On the other hand, step functions with infinite flexibility are technically difficult to realize, although it is entirely possible to arbitrarily approximate the desired function. FIG. 2b shows the curve profile of the regulator output voltage with a finite slope K2. Each voltage change of the oxygen detector is
In the curve of FIG. b, during a constant additional time Tz, the output voltage UR of the integral regulator is increased with a large slope in the direction of shifting the average λ value. Here, a value Hm=5?5, which is similarly unrelated to Tt, is obtained as the center shift. Therefore K
By selecting 2 and Tz, arbitrary deviations can be generated. It is also clear that the deviation can be carried out in the opposite direction, for example if it is desired to operate in the direction of leaner fuel-air mixture. Finally, as a special case of the embodiment of FIG. 2b, it is also possible to integrate successively by means of an integral adjuster while maintaining the initial slope k1, in order to obtain the same center deviation Hm. obviously have to work with longer additional times. In this case, for the actual deviation (for example Hm◇0.5%λ), the additional time T2 is already on the order of the engine transit time t, and the entire regulating circuit is thereby influenced too strongly. The third example shown as the first example
From the circuit shown, it can be seen that when using an oxygen detector, the necessary measures are taken in order to also obtain a mixture different from this excess air ratio by means of a sudden change at λ=1.

The circuit of FIG. 3 has a detector threshold circuit 5, the construction of which does not need to be explained in principle, but which is designed to be able to supply the detector switch voltage to the subsequent integral regulator. This detector switch voltage is switched each time the actual detector output voltage F3EUs passes through a stable characteristic point P according to FIG.

For this purpose, a comparator 6 is provided, one input of which is supplied with a constant voltage via an adjustable voltage divider consisting of resistors 7 and 8, and the other input of which is supplied with a constant voltage. , preferably via the transistor 9 to the connection point P1
A detector output voltage Us is supplied to the detector output voltage Us. Further details of the detector threshold circuit 5 do not need to be explained. The output of the comparator 6 supplies a square wave signal to the connection point P2, the state of which changes each time λ=1. The integral regulator itself is configured as an operational amplifier 15, and the non-inverting input terminal of this operational amplifier is
A constant voltage is supplied via a voltage divider consisting of resistors 16 and 17, and a detection signal is supplied to the inverting input terminal of this operational amplifier via a voltage divider consisting of resistors 19 and 20 and controllable by a transistor 18. A variable voltage is supplied depending on the device threshold voltage. On the other hand, the collector of transistor 18 is connected to both resistors 1 through resistor 21.
9 and 20 , which on the other hand is connected via a resistor 22 to the inverting input terminal of the integrator 15 . This input terminal is connected to capacitor 2
3 to the output terminal of the integrator 15, so that a voltage UR is generated at the output terminal. The output voltage resulting from the detector threshold circuit 5 reaches the base of the transistor 18 via a resistor 24. In order to be able to vary the integral action of the integrator 15 of the regulating device according to the curves of FIGS. 2a and 2b, an inverting circuit 25 comprising transistors 26 and 27 and a multivibrator circuit 28 are provided. ,
The operation of these circuits will be explained below along with a description of their configuration.

The transistor 26 of the first inversion stage is connected to the detector threshold circuit 5
When the output voltage of P2 changes to a negative value, the connection point P2
is made conductive through the resistor 30, and at this time the capacitor 3
1a, a positive voltage change is transmitted to the base of the transistor 31, or more precisely, the diode 31 connected in front of the base of this transistor is activated or deactivated, and likewise the transistor 31 is activated or deactivated. cut off

Transistor 31, together with a coupling capacitor 31a and an adjustable leakage resistor 33, is a monostable multivibrator;
Moreover, it forms a so-called economical monostable circuit, and the unstable time of this monostable circuit is
It is determined by the value of 3. Therefore, the period during which transistor 31 is in the off state can be adjusted. As soon as the transistor 31 is turned off, the diode 34 connected to the collector of this transistor becomes conductive (this diode is now connected to the negative conductor 36 via a resistor 35), so that the diode 34 becomes conductive. An additional current flows through the connected resistor 37 to the inverting input of the operational amplifier. In other words, the frugal monostable multivibrator delays the transfer of the switching pulse and at the same time conducts the diode 34 so that one input of the operational amplifier for an additional duration of this delay (unstable time) control the sides differently (signal steepening).

As a result, the output voltage of the operational amplifier, that is, the integrator 15 is
Since it changes very rapidly in the direction of positive values depending on the amount of the current, the characteristics approximately as shown in FIGS. 2a and 2b are obtained. In the embodiment shown in FIG.
Since it is desired to be independent of the normal slope of the integration process, a transistor 39 is additionally provided, which is controlled by transistor 31. When the transistor 31 is briefly cut off, the diode 40 connected to the collector of this transistor is also cut off, and the connection point between this diode 40 and another diode 41 shifts to a negative potential. . This is because this connection point is connected to the negative conducting wire 36 via the resistor 42. Via a diode 43 connected to the base of transistor 36, this transistor 39 is activated and either short-circuits the input signal at the base of transistor 18 or disconnects it. This is because the collector of transistor 39 is connected to the base of transistor 18. The integral characteristic of the integrator 15 is thus determined during the instability period of the parsimonious monostable circuit consisting essentially of the transistor 31 solely by the value of the resistor 37 (and obviously by the value of the resistor 35 to the negative conductor). (by) is definitely determined. Therefore, in the above equation for the deviation Hm, the slope K2 can be adjusted by the value of the resistor 37, and the period of delay (corresponding to the additional time Tz) before the integrator responds in the other direction can be This can be adjusted by appropriately determining the instability time of the monostable circuit.

Appropriate modifications and variations of the integrator output voltage are performed by the integrator 15.
This is also carried out when integrating in another direction, and in the embodiment of FIG. 3, it is carried out when the input voltage at point P2 becomes positive.

At this time, the transistor 26 is turned off, and the transistor 26 is turned off.
7 is conductive. This is because the base of transistor 27 is connected to negative conductor 36 via diode 45 and resistor. The voltage change at the collector of the transistor 27 is transmitted via a capacitor 46 and a diode 48 to the base of a subsequent transistor 49, which forms a second economical monostable circuit and which The collector of this transistor 49 is therefore connected via diodes 50 and 51 to the same circuit part previously described, so that the process described above is repeated. In lieu of this, I would like to point out the following.

That is, it is obvious that the entire process can be reversed in each case, so that in general it is only necessary to configure the circuit in a complementary configuration and replace the input terminals of the integrator 15, and the type of transistor used and the polarity of the feed line can be selected arbitrarily. It is also clear that this circuit operates without problems when operated with transistors of different voltage polarity and correspondingly different conductivity type. In order to ensure that the slopes at the upper and lower reversal points, respectively, are therefore the same, for example the slope K2 according to FIG. 2b, it is also possible to override the "normal slope" previously provided by the transistor 18. desirable.

According to the invention, it is therefore possible to stabilize the desired detector voltage threshold required for optimum exhaust gases due to aging of the oxygen detector and, if appropriate, due to periodic changes in the exhaust gas temperature. Even when it cannot be maintained, stable adjustments can be made.

The present invention provides approximately 300 Trt. Utilizing the stable detector voltage characteristic point occurring at V, and using this 300Tr1,V
It can also be adjusted to a desired λ value that deviates from the characteristic point.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship of the oxygen detector output voltage Js with respect to time when the fuel-air mixture changes, and Fig. 2 is a diagram showing the relationship with respect to time when the fuel-air mixture changes.
FIG. 3, a diagram showing the course of the regulator output voltage UR over time as a function of the detector voltage Us, is a circuit diagram showing an embodiment for controlling the regulation characteristic. 5...Comparison circuit, 15...Integrator, 2
5... Inversion stage, 28... Monostable multivibrator.

Claims (1)

[Claims] 1. Oxygen detector (λ detector) placed in the exhaust gas stream
A method for controlling the mass ratio distribution of a fuel-air mixture supplied to an internal combustion engine (λ adjustment) using A single integrator is provided with a detection signal in a manner that integrates to produce a controlling power regulating voltage, said power regulating voltage being shifted asymmetrically to the lean or rich side with respect to the stoichiometry of the fuel-air mixture. supplying a control voltage dependent on the detector output voltage with a delay, the integrator integration characteristic being controlled such that the integrator continues to integrate in the same direction for a predetermined period of time after the original detector switching point; and further controlling the integrator during said predetermined period of time such that a sudden steepening of said integrator output signal U_R occurs in the direction of a new desired adjusted average λ value. A method for controlling the mass ratio distribution of a supplied fuel-air mixture. 2. Internal combustion engine according to claim 1, characterized in that the current supplied to the input of the integrator is changed in each case at the beginning of a predetermined period formed by the delayed supply of the control voltage to the integrator. A method for controlling the mass ratio distribution of a fuel-air mixture supplied to a fuel-air mixture. 3 an oxygen detector (λsonde) arranged in the exhaust gas stream of the internal combustion engine, which generates as an output voltage an actual value signal of the mass fraction of the fuel-air mixture supplied to the internal combustion engine; and integrating means to which the output signal of the detector is applied to generate a power adjustment voltage that is asymmetrically shifted in the lean or rich direction in relation to the stoichiometric mass ratio distribution of the fuel-air mixture. In the device for controlling the mass ratio distribution of the fuel-air mixture supplied to the device, at least one delay device is provided, the delay device comprising:
Controlled at least indirectly by the output signal of the detector, an integrator 15 connected downstream is provided with an adjustable duration of the instability period of the delay device after the switching point determined by the detector. for a period of time, controlling said integrator to continue integrating in the same integration direction for said duration, and additionally for a duration defined by said delay device, at the input of the integrator; Mass ratio distribution of a fuel-air mixture supplied to an internal combustion engine, characterized in that the control signal is applied in such a way that a steep change in the integral slope and thus in the integrator output signal occurs during said duration. A device that controls