JPH0373742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method and apparatus for lambda control of an internal combustion engine, and more particularly, a method and apparatus for controlling lambda of an internal combustion engine, and more particularly, the control data between at least two switching points of a lambda sensor are converted into operating parameters such as load, rotational speed, time, etc. The present invention relates to a lambda control method and apparatus for an internal combustion engine that performs lambda control by adjusting the lambda according to the operating characteristics (hereinafter referred to as operating characteristics).

Lambda control devices for internal combustion engines in automobiles have already become standard equipment in many countries today, where relatively strict exhaust gas regulations have been enacted. The lambda control device is equipped with an exhaust gas sensor (lambda sensor, oxygen sensor), and the sensor switches so that the lambda value (air ratio, that is, the ratio between the amount of supplied air and the amount of air required) of the mixture becomes "1". This switching operation is carried out by continuously enriching or diluting the air-fuel mixture. The lambda sensor has a response time and takes time to change the mixture composition, resulting in undesirable exhaust gas peaks. If the mixture is allowed to become slightly richer, it may take a longer time to reach the next switching point. In the opposite case, i.e. when the mixing switch is highly enriched, the delay time between the mixture and the exhaust gas causes an overshoot, which results in a peak value of the exhaust gas.

In the lambda control device disclosed in German Patent Publication No. 2206276, the time between two switchings is measured, and if the period of no switching continues for a predetermined period of time, the control amplifier time constant changes to another shorter value. can be switched to As a result, after this predetermined period of time has elapsed, the air-fuel mixture changes more strongly, and therefore the switching becomes faster. Of course, in this case there is a risk of a kind of overcontrol with the emission of undesirable exhaust gases.

Even if fully satisfactory results are obtained with these known control devices, peak values of the exhaust gas inevitably appear, so that with conventional solutions it is not possible to obtain optimal values in terms of cleaning the exhaust gases. The drawback is that it cannot be done.

The present invention was made in view of the above circumstances, and
It is an object of the present invention to provide a lambda control method for an internal combustion engine and a device therefor, in which clean exhaust gas can always be obtained and optimum lambda control can be performed without generating undesirable exhaust gas peak values.

To achieve this objective, the present invention provides an internal combustion engine with lambda control by adjusting control data between at least two switching points of a lambda sensor according to operating parameters such as load, rotational speed, time, etc. In the lambda control method, the integration of the lambda controller is performed according to the duration of the period from the end of the previous period to the present and the length of the previous period whose start and end points are determined by changes in the sensor potential occurring at the switching point. We adopted a configuration that changes the slope.

The present invention also provides at least two lambda sensors.
In a lambda control device for an internal combustion engine, which performs lambda control by adjusting control data between switching points according to operating parameters such as load, rotational speed, time, etc., a lambda sensor and a lambda control device according to a signal from the lambda sensor are used. Detects the duration of the period from the end of the previous period to the present, and the length of the previous period, whose start and end points are determined by the lambda controller that controls the value and the change in sensor potential that occurs when the lambda sensor switches. and means for changing the integral slope of the lambda controller according to the detected continuation length up to the present time and the length of the previous period.

Embodiments of the present invention will be described in detail below based on the drawings. The following embodiments will be explained by taking as an example a fuel injection device that operates intermittently. However, such lambda λ control is independent of the air-fuel mixture supply method;
For example, it can also be used in a device using a vaporizer.

In FIG. 1, reference numeral 10 indicates a time signal generator, and the time signal generator 10 receives input signals from a load sensor 11 and a rotational speed sensor 12 and emits a reference injection pulse having a pulse width tp on the output side. A correction circuit 13 is connected downstream of the time signal generator 10, and within the correction circuit 13 the reference injection pulse is corrected according to the temperature θ of the internal combustion engine and by lambda control. This corrected pulse is applied to at least one injection valve 1 arranged in the region of the intake pipe of the internal combustion engine.
4.

Reference numeral 15 indicates a lambda sensor (a sensor that measures oxygen components in exhaust gas). lambda sensor 15
issues an output signal to the lambda controller 16, which output signal is corrected in the lambda controller 16 via a control input signal 17 by other characteristics to form a lambda correction signal, which lambda correction signal is input to the correction circuit 13. Used as an input signal.

The basic configuration shown in FIG. 1 is known per se. A reference injection pulse is formed as a function of the load and the rotational speed, the reference injection pulse is subsequently corrected as a function of other operating characteristics of the internal combustion engine, and is then used as a drive signal for the electromagnetic injection valve.

Figures 2A and 2B illustrate the invention.
FIG. 2A shows the output signal of the lambda sensor 15 when the composition of the air-fuel mixture changes, and FIG. 2B shows the integrated output signal of the lambda controller 16 of FIG. 1. . The integrator in the lambda controller 16 integrates upwards or downwards according to the plus or minus of the potential in FIG. 2A, i.e. depending on whether a rich or lean mixture is present. .

In the case of this embodiment shown in FIG. 2, the integrator integrates upward when the output signal of lambda sensor 15 is positive, and integrates downward when it is negative. What is important is that the integral slope changes according to the relationships up to and after the switching time of the lambda sensor 15. This is clear from the equation written in Figure 2B. According to this, the slope between periods is determined at least by the duration of the period and its slope. Further, the slope is changed as time passes after switching.

Expressed in a general formula, m _i =f(t _i -1, t _i , m _i -1, n, Q). However, t _i-1 = Total duration of the previous integration period t _i = Current duration from the previous switching point m = Integral slope n = Rotational speed Q = Integration taking into account load optimization The gradient of is selected as follows. In other words, the selection is made such that the longer the time that the preceding sensor potential remains at a constant value, or the longer the duration of the current constant output potential, the larger the subsequent slope value becomes. As a result, the integral component of the control device is continuously increased or decreased to a given maximum or minimum value. In addition to being related to pure time in this way, the integral component can also be increased even when the lambda sensor is not switched during a predetermined number of rotations of the crankshaft. In that case, the integral component is reduced when switching takes place.

Furthermore, it is also possible to vary the slope value in relation to the load signal or the rotational speed signal, in particular to prevent the control device from becoming unstable at limit values.

FIG. 3 shows an embodiment of the lambda control method according to the invention. FIG. 3 is a detailed diagram of the circuit configuration of the lambda controller 16 shown in FIG. An integrator 26 is shown in each case. Whenever the potential changes in the lambda sensor 15, a switching signal is generated at the first output terminal 28 of the signal processing circuit 20. At the second output terminal 29 of the signal processing circuit 20, a signal is generated indicating whether the sensor signal is at a high or low potential. The output terminal 28 is the reset input terminal of the counter 23, the input terminal of the gate circuit 21, and the downward input terminal 3 of the shift register 24.
Connected to 0. On the other hand, sensor signal processing circuit 2
The second output terminal 29 of 0 is connected to the integration direction control input terminal of the integrator 26 . This integrator 26
furthermore has an input terminal 31 via which it is possible to fix the integral value of the integrator 26.

A rotation speed signal is inputted to the count input terminal 32 of the counter 23 from a rotation speed sensor (not shown). The output of the counter 23 is connected to an upper input terminal 34 of the shift register 24, an input terminal of the gate circuit 21, and a transfer input terminal 35 of the counter 23. The shift register 24 is connected and controlled via a lead 36 to a downstream power supply 25, which in turn is controlled via a further input 37 in relation to the load. In the embodiment of FIG. 3, the power supply 25
has a direct effect on the slope of the integrator 26 whose output is led to the correction circuit 13.

Reference numeral 40 indicates a second counter, and this counter 40 is also reset by a signal from the output terminal 28 of the sensor signal processing circuit 20.
Count the number of times 3 becomes zero. In this embodiment, the output terminal of the counter 23 is directly connected to the count input terminal 41 of the counter 40. Furthermore, in the case of this embodiment, the counter 40 is
2 control input terminal 42 or shift register 24
is connected to either one of the control input terminals 43 of.

The operation of the lambda control device shown in FIG. 3 will be explained below.

Lambda sensor 15 signal changes from “0” to “1”
and vice versa, a pulse is generated from the output terminal 28 of the sensor signal processing circuit 20.
This pulse controls the gate circuit 21 and the counter 23, so that the value stored in the memory 22 is transferred to the counter 23. counter 23
is subtracted from this value each time a rotation speed pulse is sent to the counter input terminal 32.

When the counter 23 reaches counting state "0", the shift register 24 is shifted to the next higher digit. Furthermore, the gate circuit 21 and the counter 23 are controlled via an input 35 so that the value of the memory 22 is transferred from the memory 22 into the counter 23 again.

If a pulse is generated at the output terminal 28 of the sensor signal processing circuit 20 before the counter 23 counts up to "0", the value stored in the memory 22 is loaded into the counter 23 again. Furthermore, the shift register 24 is shifted downward by one place.

The output signal of shift register 24 controls power supply 25 . The higher the digit of the shift register 24, the higher the power supply of the power supply 25, which increases the slope of the signal of the integrator 26.

In the case of lambda control, the integration direction of the integrator 26 is normally switched upward or downward depending on the sensor voltage. Via a special control input 31, the value of this integrator 26 can be switched and kept constant. This is done during warm-up at startup, during acceleration, and during deceleration.

The control of the integral slope described above allows the lambda controller to always operate with the smallest possible integral component. Furthermore, when a large deviation must be compensated for, the integral component can be quickly increased. Thereby, the control range of lambda control can be expanded.

According to another embodiment of the lambda control device according to the invention, it is possible to determine how many times the counter 23 reaches zero after the output terminal 28 of the sensor signal processing circuit 20 is output before the next switching of the lambda sensor. The counter 40 counts. According to this counting result, the output value of the memory 22 is increased or decreased.

In the above description, the counter 32 is the memory 2
The load value from 2 is subtracted by the rotation speed n, and each time it reaches zero, the shift register 24 is shifted to change the integral slope, so the continuous length ti from the end of the previous period to the present is Therefore, the integral gradient is changed. In addition, the counter 40
The counter 32 counts how many times the counter 32 reaches zero and changes the output value of the memory 22.
When the output value from the memory 22 is loaded into the memory 22, since the output value of the memory 22 is a value indicating the length of the period, the value of the counter 32 changes according to the length of the previous period. , therefore the integral slope will also change according to the length of the previous period. Furthermore, since the shift position (indicating the integral slope) of the shift register 24 is maintained when changing from ti-1 to ti, the integral slope mi of the period ti follows the integral slope of the previous period. It's going to change.

Furthermore, the following is also possible. That is, as indicated by selection switch 45, counter 2
3 reaches zero, the shift register 24 is strongly shifted, and as a result, the power supply 2
5 can be directly controlled, thereby controlling the slope of the integral signal.

Although FIG. 3 shows an embodiment in which the method of the present invention is implemented using hardware, there is no problem in achieving the object of the present invention with a configuration using a programmable computer. This is because the present invention is clearly understood, and it is easy for those skilled in the art to solve the problems by using a computer and a program based on the hardware configuration shown in FIG. .

In the example shown above, the principle of combining lambda control with integral component control was explained apart from the application aspect, but below, an example will be explained where lambda control is performed during operation in a "quasi-steady state". The basic idea is to treat lambda control separately in steady and unsteady operating states, and to shift from control with lambda control to control without lambda control when quasi-steady operating states persist. This is what I did. Since the control target is complex, a computer-controlled configuration was adopted.

FIG. 4 schematically shows the main parts of the computer-controlled configuration. Reference numeral 50 is a central processing circuit
Indicates CPU, data line, control line, address line 5
1 to a memory 52 and an input/output port 53. The input/output port 53 receives various input signals I _i in addition to the signals from the lambda sensor 15 and outputs various output signals O _i , such as injection time and error signals.

FIG. 5 shows the block configuration of a lambda controller using computer control. Here, the operating characteristic input I _i is the integrator 5 as well as the lambda sensor 15.
6 is connected to a Δ (deviation) detection unit 55. The output of the integrator 56 is output from an adding circuit (reference numeral 57 in FIG. 5) as in the fuel supply amount control device in FIG.
).

At the beginning of the quasi-steady region, the deviation detection unit 55 inputs operating characteristics such as rotational speed n and air amount.
Q〓 or engine temperature T, etc. are stored. Furthermore, signals derived from the input variables in the control device are also used as input signals.

The deviation of one of these operating characteristics is given a value ΔI _i
As soon as this is exceeded, a changeover takes place in the deviation detection unit 55, so that in each case the instantaneous value of the input variable I _i is transferred to the corresponding memory. A signal for the unsteady region is output to the deviation detection unit 55. Furthermore, for each detection time, the value of the driving characteristic input I _i at that time is changed to the driving characteristic input I _i (t _o
−1). When the deviation becomes smaller than the predetermined value ΔI _i again, the deviation detection unit 55 outputs a signal for the quasi-steady operation region,
The last lambda value encountered is retained as the valid value.

The method is shown in FIG. 6, but it has also been found to be effective to form an average value for different devices. In FIG. 6, various lambda values are plotted against time, the lambda values detected at a given time being averaged and used to carry out the lambda control as precisely as possible. The formation of this average value is determined, for example, by correction values K1, K2.

The correction value K1 characterizes the deviation of the values stored during operation from the minimum value, whereas the correction value K
2 indicates the deviation from the maximum value. The average value M shown in the figure indicates a lambda value used as a new control value for lambda control.

In other words, when the slope of the integral reaches the minimum value due to the lambda control described above, the correction value K is set at both switching points of the lambda controller, as shown in FIG.
1, K2 are stored. An average value M of these correction values K1 and K2 is formed and the lambda controller is switched off. Of course, it is also possible to form the average value from more than two correction values or on the basis of the average value itself.

The average value thus formed becomes the correction value for the lambda value "1". In the central processing unit 50, from this correction value and the basic value stored in the memory 52, a total value corresponding to the fuel supply amount that is adjusted to have a lambda value of "1" is determined.

If a value of lambda that is not equal to "1" is desired, this value is accordingly multiplied by the desired lambda value at the respective operating point and thereby the fuel supply quantity is determined. In this way, any lambda value can be generated at each operating point.

If the characteristics of various functions, such as start-up enrichment, warm-up enrichment, etc., are stored digitally, the stored characteristics are corrected as follows.

If only the values for lambda value = "1" are corrected, an average value is formed as described above. At that time, the value of the characteristic curve is corrected by the determined correction value without interrupting the lambda controller,
This corrected value is memorized so that a learning effect can be obtained.If the value is corrected when the lambda value is not equal to "1", after reaching the slope of the minimum integral, it is again averaged. The formation takes place, the lambda controller is switched off, and the sum value corresponding to the fuel supply corrected to the desired lambda value is calculated, as described above. This value is then stored as the control value at the current operation time instead of the previous value. Furthermore, this value is used to control the fuel supply amount until unsteady operation is detected again. The fuel supply amount is determined by the stored value at the respective operating point. When the deviation detection circuit is returned to normal operation, the integral value is set to zero and lambda control is restarted at a predetermined gradient value. In this way, the integral gradient is optimized and the above-mentioned lambda control is performed.
Once the integral slope has reached the smallest possible value, the formation of the correction value takes place again and the value of the fuel supply quantity stored for the corresponding operating point in time is corrected.

As explained above, in the present invention, the integral slope of the lambda controller is changed according to the duration of the period determined between the switching points of the lambda sensor from the end of the previous period to the present, and the length of the previous period. This allows the integral slope to be continuously optimized and quickly set to the desired value, resulting in cleaner exhaust gases and optimal lambda control.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing the overall configuration of a fuel supply amount control device for an internal combustion engine to which the method and device of the present invention are applied, and FIG. FIG. 2B is a signal waveform diagram showing the output signal, and FIG. 2B is a signal waveform diagram showing the signal of the integrator of the lambda control device in FIG. 4 is a block circuit diagram showing the configuration of one embodiment, FIG. 4 is a block circuit diagram showing the main part configuration of another embodiment using a microcomputer, and FIG. 5 is a block circuit diagram showing the overall schematic configuration of the embodiment using a computer. FIG. 6 is a diagram illustrating a method of selecting a lambda control value by forming an average value. 15... Lambda sensor, 16... Lambda controller, 20... Signal processing circuit, 21... Gate circuit, 22... Memory, 23, 40... Counter,
24...Shift register, 26...Integrator, 50
... central processing circuit, 52 ... memory, 53 ... input/output port, 55 ... deviation detection unit, 56 ...
...Integrator, 57...Correction circuit.

Claims (1)

[Claims] 1. A lambda control method for an internal combustion engine, which performs lambda control by adjusting control data between at least two switching points of a lambda sensor according to operating parameters such as load, rotational speed, time, etc. The integral slope of the lambda controller according to the duration ti from the end of the previous period to the present and the previous period length ti−1 of the period whose start and end points are determined by changes in the sensor potential occurring at the switching point. A lambda control method for an internal combustion engine characterized by changing mi. 2. The lambda control method for an internal combustion engine according to claim 1, characterized in that the integral gradient mi is changed according to a gradient value in the previous period. 3. The internal combustion engine according to claim 1 or 2, wherein the integral slope is switched to a larger value when the period becomes longer, and to a smaller value when it becomes shorter. Lambda control method. 4. A lambda control method for an internal combustion engine according to any one of claims 1 to 3, characterized in that the integral gradient is changed in accordance with a load. 5. Claims 1 to 3, characterized in that the integral gradient is changed according to the rotational speed.
Lambda control method for an internal combustion engine according to any one of the preceding paragraphs. 6. The method according to any one of claims 1 to 5, characterized in that when the integral gradient reaches a minimum value, the average value of the lambda values at the two switching points is determined. Lambda control method for internal combustion engines. 7. The internal combustion engine according to claim 6, wherein when the integral gradient reaches a minimum value, lambda control is interrupted and the fuel supply amount is corrected using the average value of the lambda values. Lambda control method. 8. A lambda control device for an internal combustion engine that performs lambda control by adjusting control data between at least two switching points of a lambda sensor according to operating parameters such as load, rotational speed, time, etc., comprising: a lambda sensor 15; A lambda controller 16 that controls the lambda value according to a signal from the lambda sensor, and the duration of the period from the end of the previous period to the present, the start and end of which are determined by changes in the sensor potential that occur at the time of switching the lambda sensor.
ti and the length of the previous period ti−1; and means for changing the integral slope of the lambda controller according to the detected duration of the current period and the length of the previous period. A lambda control device for an internal combustion engine, characterized by: 9. The lambda control device for an internal combustion engine according to claim 8, further comprising means for changing the integral slope of the lambda controller in accordance with the slope value in the previous period. 10. The internal combustion engine according to claim 8 or 9, wherein the integral gradient is switched to a larger value when the period becomes longer, and to a smaller value when it becomes shorter. Lambda controller.