JPH03210042A - Air-fuel ratio control unit for engine - Google Patents

Abstract

PURPOSE:To control the stable state of an engine by determining the mutual correlation function between the fine pseudo irregular signal superimposed on the fuel injection quantity and the stability-related output, and increase/ decrease-correcting the fuel so that it coincides with the preset target value. CONSTITUTION:The periodic fine pseudo irregular signal from a generating device 26 is superimposed on the basic injection quantity from a calculating signal 23 by a superimposing means 27. The mutual correlation function between the pseudo irregular signal and the stability-related output of an engine detected by a detecting means 28, e.g., rotation change rate, torque change rate, and change rate of effective pressure, is calculated by a calculating means 29, whether it coincides with the preset target value Rs or not is judged, and the fuel increase/decrease correction quantity for the coincidence is determined by a calculating means 31. The increase/decrease correction quantity is added to the basic injection quantity from the calculating means 23, and the injection quantity is determined by a determining means 32. The engine can be controlled near the stability limit, not in the unstable state beyond the stability limit.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an air-fuel ratio control device for an engine.

(Prior art) For example, in a lean burn engine, in order to improve fuel efficiency, there is a device that controls the air-fuel ratio to a level close to the limit where the engine can stably OUT. JNo.

(see 4).

To explain this with Figure 10, as shown in the upper part of the figure, as the fuel injection pulse width (fuel amount) is gradually reduced, the air-fuel mixture becomes leaner and the combustion condition deteriorates. Accordingly, the rotational fluctuation rate increases as shown in the middle row of the same figure. In this case, a slice level is set at a position where the rotational fluctuation rate should not increase any further, that is, at the stability limit, and this slice level and the actual rotation are By comparing with the variation rate, it is shown if the actual rotation variation rate exceeds the slice level.

The control device that receives this lower determination signal increases the fuel injection pulse width by a certain width in steps when the time at the /'% level exceeds a predetermined value To. Then, the fuel injection pulse width is gradually decreased again and the above process is repeated. As a result, the engine is controlled at an air-fuel ratio near the limit that allows stable rotation.

(Problem to be Solved by the Invention) By the way, in such a device, the injection amount is increased only after the time exceeding the slice level has passed a predetermined TO. ,
It is unavoidable that large rotational fluctuations will occur. In other words, unless a certain degree of rotational fluctuation is intentionally caused (such rotational fluctuation is referred to as ergonomics), it is not possible to control the engine to near the limit at which it can rotate stably. In particular, in Lean Burn Ennon, combustion is performed with a lean mixture to begin with, so reducing the injection amount in order to search for the stability limit may cause the engine to stop due to rotational fluctuations.

On the other hand, there are devices that can determine whether the engine is rotating stably without pushing the engine to its stability limit. For example, by determining the crank angular position θpIIa at which the cylinder pressure is maximum from the detected value of the cylinder pressure sensor, and comparing the variance value of this crank angular position θρwax with a predetermined value, the variance value is within the predetermined value. If it does not fall within this range, it is determined that the engine is not rotating stably.

However, in this device, the device for detecting and processing the cylinder pressure is expensive.

This invention was made in view of these conventional problems, and by using a correlation method using pseudo-irregular signals, it is possible to drive the engine to its stability limit at low cost and without causing large rotational fluctuations. The purpose is to provide a device that can be controlled in the vicinity.

<Means for Solving Problem S) As shown in FIG. Means 23 calculates the basic injection amount Tp based on the fuel injection amount ffi! In the air-fuel ratio control device for an engine, the device 26 generates a periodic minute pseudo-irregular signal (for example, an M-series signal).
and a means 27 for superimposing this pseudo-irregular signal on the injection amount signal; and a means 27 for superimposing this pseudo-irregular signal on the injection amount signal; (variation rate of interleaved mean effective pressure)
a means 28 for detecting y; a means 29 for calculating a cross-correlation function φ9y between the output y and the pseudo-irregular signal; and a means 29 for calculating whether this cross-correlation function φ'xY matches a predetermined target value R5. and means 3 for calculating a fuel increase/decrease correction amount HO8 so that the cross-correlation function φ9y matches a predetermined target value R5 according to the determination result.
1, and a means 32 for correcting the injection amount Tp with this increase/decrease correction amount HO8 to determine the fuel injection amount to be output (operation). By the cross-correlation function φ'xy of gender-related output y,
The degree to which the engine rotates stably or not can be determined.

Then, the fuel injection amount is corrected to increase or decrease so that this output φ9y matches the target value R5, which is determined as a value near the limit that allows the engine to rotate stably.

In this way, the engine is controlled to be close to the stability limit, but the actual engine does not exceed the stability limit during this control.

(Example) Figure 2 shows the mechanical configuration.
- The intake air amount Qa is measured by the meter 2, and the crank angle sensor 3
The engine speed Ne is detected by the air-fuel ratio sensor 4, and the air-fuel ratio in the exhaust gas is detected by the air-fuel ratio sensor 4, and these signals are input to the control unit 51.

Co1 P that supplies the fuel injection amount signal to the InnoEctor 6
−ζ上kenri硼? p1. % l Kin ζ
The actual engine is controlled to near the stability limit according to the method shown in M.

Figure 3 shows a routine for superimposing the M-series signal, which is one of the IIl-like irregular signals, on the injection amount signal.Sl checks whether the operating conditions are in a steady state, and if the operating conditions are in a steady state, it is sent to S2. move on.

S2 is a part that performs the function of the signal superimposing means 27 in FIG. 1, and here superimposes the M sequence signal 9(t) on the fuel injection pulse width (described later) T iB [msl] calculated by the conventional device. In other words, in this case, the fuel injection pulse width Ti[
[transport S] is T i = T iB ten odor (1)...■. This T
When i is given to injector 61, injector 6
During this period, fuel is injected into the engine's intake boat. Note that Ti is output from an interface within the control unit, and this interface performs the function of the output means 24 in FIG. 1.

On the other hand, in S3, Ti=TiB.

As shown in the upper part of FIG. 6, the MA column signal 9(t) has an amplitude aSR small pulse width Δ, a period NΔ (N is the maximum sequence and is 15 in the example, but 7 and 31 can also be used)
is a periodic function with parameters. Therefore, the autocorrelation function φ(τ) is also a periodic function, and becomes a narrow triangular periodic pulse train as shown in the lower part of FIG. This MJ1% column signal is a minute signal, and even if it is superimposed on the injection amount signal, the engine rotation will not vary greatly and will not impair the driver's driving sensitivity. Note that the signal is not limited to the M-sequence signal, and any periodic pseudo-irregular signal such as an L-sequence signal or a twin prime number sequence signal may be used.

FIG. 4 shows a routine for determining whether the actual engine condition is near the stability limit and determining the fuel increase/decrease correction amount in accordance with the determination result.

In the Sll, data of the M-sequence signal and the rotational fluctuation rate y based on this input are inputted and stored at a constant cycle.

The rotational fluctuation rate y is determined from the engine rotational speed Ne.

When the change in the rotational speed Ne is shown in FIG. 7, the rotational speed fluctuation rate y is calculated using the following formula, where the rotational speed change per fixed section is set as ΔNe.

y=ΔNe/'i4e...■ However, e is the average rotation speed.

Note that the output extracted from the engine when the MiA column signal 9 is superimposed is not limited to the rotation fluctuation rate, but may be output related to the stability of the engine such as the torque fluctuation rate or the fluctuation rate of the indicated average pressure Pi. It doesn't matter.

In S12, it is checked whether data input for one cycle of the MPS string signals 9 and y has been completed, and if it has been completed, the process advances to S13.

S13 is a part that performs the function of the cross-correlation function calculating means 29 in FIG. In this case, deinotal signal processing is performed, so the right side of equation (2) can be replaced by the integrated value. In other words,
The actual control system consists of a discrete value system.

S14 and 615 are parts that perform the function of the determiner 830 in FIG. 1, and 816 to 818 are the increase/decrease correction amount calculating means 3 in FIG.
This is the part that fulfills the function 1. In S14 and S15, S
By comparing the cross-correlation function φ2yCα) obtained in step 13 with the predetermined target value R5±Δ, φ2y(α)〉R5+Δ
(However, if Δ is a constant value), it is determined that the enon rotation is less stable than the target value, and the process proceeds to S16, where the increased amount ZOU is added to the correction amount HO8. Conversely, φQy(α
)<R5-Δ, it is determined that the engine can rotate stably even if the fuel is reduced, and the process proceeds to S17, where the reduced amount GEN is subtracted from the correction amount HO8, R5-Δ≦φ2y<6)≦
If R, 10Δ, it is assumed that it is in the dead zone, and the process proceeds to step 318, where neither increase nor decrease is performed. Note that the correction amount HO8 is a value that is preset according to the engine load and rotation speed.

The reason why the increase or decrease in fuel is calculated according to the comparison result between φ9(α) and R5±Δ is as follows. In a region where the engine rotates stably, the rotational fluctuation rate will not increase even if the injection amount is slightly changed.

That is, in this case, there is no mutual relationship between the injection amount and the rotational fluctuation rate (the value of the cross-correlation function φ9y(α) is close to 0). However, when the engine approaches the limit at which it can be rotated stably, the combustion state has a large effect on the stability of the engine, and even a small change in the injection amount causes a large change in the rotational fluctuation rate. In other words, in this case, the mutual relationship between the injection amount and the rotational fluctuation rate becomes close (φ′
xy(ff) approaches 1). This means that the value of the cross-correlation function φ) represents the degree to which the engine is stably rotating.

Therefore, if an attempt is made to control the engine near the stability limit, the value equivalent to the cross-correlation function when the engine is operated near this limit is set as the target value R5, and φ9y(a)>R
In the case of s + Δ, the air-fuel ratio of the air-fuel mixture is enriched to stabilize combustion, and conversely, in the case of φ9 α) < Rs - Δ, the air-fuel ratio is made lean to bring it closer to the stability limit side. All you have to do is do it.

Fig. 5 shows mnqt which corresponds to when the injector 6 opens.
This is a routine for calculating m pulse width TiB.

S21 and 22 are parts that perform the function of the basic injection amount calculation means 23 in FIG. 1, and in S21, the intake air amount Qa and the rotation speed N
e is read, and in S22 the basic injection pulse width T p (:
Calculate K-Q a/N e, where K is a constant.

You can also refer to a map to find Tp[msl.

S23 is a part that performs the function of the injection amount determining means 32 in FIG. 1, and here the fuel injection pulse width TiB is calculated using the following equation.

TiB==(Tp+HO3)XCo+Ts=■However,
■In the formula, Co is the sum of 1 and the water temperature increase correction coefficient, etc., and T
s is the invalid pulse width.

Formula (2) is a method of adding HOS to Tp, but a multiplication format may also be used.

According to this equation (2), when HOS>0, the air-fuel ratio is made richer than the air-fuel ratio determined by Tp, and conversely, when HOS<O, the air-fuel ratio is made lean.

Figures 3 to 5 show the CPU in the control unit.
This is shown as a routine given to the system, but when constructed as a block diagram, it becomes as shown in FIG. 9.

Here, the operation of this example will be explained.

In this example, the degree to which the engine is rotating stably is determined by the cross-correlation function φ'xy ((H) between the M-sequence signal 9 that slightly changes the injection amount and the rotational fluctuation rate y. This is because the closer the engine approaches the limit for stable rotation, the closer the correlation between the injection amount and the rotational fluctuation rate becomes, and the value of the cross-correlation IgIfItφ1Qy (α) increases.

When the value of φQy(α) exceeds the target value R5, which is determined as a value near the limit that allows the Ennon to rotate stably, the correction amount HO3 increases, and the amount of fuel injected from the injector 6 is increased by that amount. Conversely, the value of φ9α) is R
If the value is smaller than 5, the value of correction jlHO8 will decrease, and the value of engine φ2y(α) will be set to match R5, that is, near the limit where the engine can rotate stably. controlled to the set target value.

Therefore, as shown in FIG. 8, the rotational fluctuation rate does not exceed the stability limit, but settles down at a position with a little margin from the stability limit.

In other words, in this example, when controlling to a target value set near the stability limit, there is no need to go out of your way to exceed the stability limit.

In contrast, in the conventional example, control to near the stability limit is possible only after the stability limit is exceeded.

Although the Mih train signal is superimposed during operation in order to check whether the engine is near the stability limit, this signal is very small, and since it is performed during steady operation, it produces a negative effect on the engine. This point is especially important when it comes to lean burn engines. In a lean burn engine, in order to determine whether or not the stability limit is reached, the injection
-1) Export - ``-111+h+1rノ11 Yu, L does not stop, and it is possible that the engine will stop.

In addition, all processes such as generating M-sequence signals and calculating cross-correlation functions are performed by Microcombi.

- It can be done by a third party, so there is no cost increase.

Finally, the increase/decrease correction amount HO6 can also be configured as a learned value.

(Effect of the invention) This invention uses a correlation method by superimposing a pseudo-irregular signal to obtain a cross-correlation function between the pseudo-irregular signal superimposed on the injection amount and the stability-related output, and this function is calculated in advance. Since we decided to increase or decrease the fuel to match the set target value,
This can be achieved by controlling Ennon to near the stability limit without leaving it in an unstable state exceeding the stability limit.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of this invention, Fig. 2 is a system diagram of one embodiment, Figs. 3 to 5 are flowcharts for explaining the control operation of this embodiment, and Fig. 6 is an M-sequence signal. ? (
t) and the autocorrelation function φ99(τ) of this signal, FIG. 7 is a waveform diagram for explaining the calculation of the rotational fluctuation rate of this embodiment, and FIG. 8 is a waveform diagram showing the operation of this embodiment. ! A waveform diagram for clarity, FIG. 9 is a control block diagram of another embodiment,
FIG. 10 is a waveform diagram of a conventional example. 2...Air 70-meter (engine load sensor), 3
...Crank angle sensor (engine speed sensor), 5
...Control unit, 6...Injector (
fuel injection device), 21...engine load sensor, 22
... Engine rotation speed sensor, 23 ... Basic injection amount calculation means, 24 ... Output means, 25 ... Fuel injection device, 26 ... Pseudo-irregular signal generation device, 27 ... Signal superimposition Means, 28...Stability related output detection means, 29.
... Cross-correlation function calculation means, 30 ... Judgment means, 31
. . . Increase/decrease correction amount calculation means, 32 . . . Injection amount determination means.

Claims (1)

[Claims] A sensor that detects the engine load and rotation speed,
A device for generating a periodic minute pseudo-irregular signal in an engine air-fuel ratio control device comprising means for calculating a basic injection amount based on these detected values and means for outputting this injection amount to a fuel injection device. means for superimposing this pseudo-irregular signal on the injection amount signal; means for detecting an output related to engine stability that slightly changes due to the superimposition of this pseudo-irregular signal; means for calculating a cross-correlation function between the two from the regular signal; means for determining whether the cross-correlation function matches a predetermined target value; and means for determining whether the cross-correlation function matches a predetermined target value according to the determination result. An engine characterized in that it is provided with means for calculating a fuel increase/decrease correction amount so that they match, and means for correcting the injection amount using the increase/decrease correction amount to determine the fuel injection amount to be output. Air-fuel ratio control device.