JP3679938B2 - Signal processing method of heating resistor type air flow meter for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion control method for an internal combustion engine using a heating resistor type air flow meter, and relates to a control device and method for accurately converting an output signal of the heating resistor type air flow meter into an intake air flow rate.
[0002]
[Prior art]
The output signal of the heating resistor type air flow meter is non-linear due to the operating principle of the heating resistor type air flow meter, and the intake pulsation that occurs in the intake state of the internal combustion engine and the reverse air flow associated therewith In the generation region, the measurement error of the air flow rate was large.
[0003]
Therefore, in an internal combustion engine combustion control apparatus using a heating resistor type air flow meter, this region is detected and the output signal of the heating resistor type air flow meter is corrected or ignored so that the intake air amount is hypothesized. Thus, combustion control was established. Alternatively, the heating resistor type air flow meter itself has been devised to reduce errors.
[0004]
However, reducing the error in the heating resistor type air flow meter itself has been in the direction of adding parts around the heating resistor type air flow meter and increasing the calculation load of the combustion control system.
[0005]
[Problems to be solved by the invention]
Since the output signal of the conventional heating resistor type air flowmeter is a heating resistor type, it has a non-linear output signal with respect to the intake air flow rate that should be detected theoretically.
[0006]
At the same time, it takes time to heat and dissipate the heat generation resistor. When this signal is simply smoothed and converted into the intake air flow rate, there is a region where a large error occurs depending on the state of the air to be measured.
[0007]
The error that occurs here is ignored in combustion control, or by using a high-speed response heating resistor air flow meter, the output signal of the heating resistor air flow meter is captured and converted to air flow in a short time. Has been.
[0008]
However, if the error is ignored, the combustion control becomes appropriate and the result of the control becomes unintentional. If a high-speed heating resistor type air flow meter is used, the combustion control is performed accurately, but the processing program of the combustion control system is complicated. There is a drawback that the processing load increases.
[0009]
An object of the present invention is to provide a signal processing method for a heating resistor type air flow meter for an internal combustion engine that can reduce a measurement error during intake pulsation with a small load.
[0010]
[Means for Solving the Problems]
The object is to convert the signal of the heating resistor air flow meter into a flow rate value, and to increase the delay amount at a high wave height of the instantaneous flow rate value, and to delay the delay at a low wave height of the instantaneous flow rate value. This is achieved by a signal processing method for a heating resistor type air flow meter for an internal combustion engine, comprising a variable filter amount search step for reducing the amount, and a flow rate filtering step for delaying the flow rate value based on the delay amount .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the contents of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 shows a combustion control system for a general internal combustion engine.
[0013]
In a series of operations of the internal combustion engine, the intake air is sucked from the air cleaner 9, the flow rate is restricted by the throttle 3 through the air flow meter 2, and the intake air is guided to the intake manifold 10. An appropriate amount of fuel calculated by the control unit 1 according to the air flow rate detected by the air flow meter 2 is sprayed from the injector 4 and sucked into the cylinder. Furthermore, an electric spark is generated with a spark plug at an appropriate timing to ignite and explode the fuel.
[0014]
The energy generated by this explosion is converted into rotational force by the crank 12. After the explosion is finished, the exhaust gas after combustion is released from the exhaust valve 13.
[0015]
Currently, a heating resistor type air flow meter that is generally used may generate a measurement error in the operating state of the internal combustion engine due to the following factors.
[0016]
(1). In principle, the heating resistor type air flow meter has a non-linear output characteristic with respect to the intake air flow rate.
[0017]
(2). There is a slight delay in the instantaneous response due to the heat dissipation characteristics of the heating resistor.
[0018]
Here, a specific error generation mechanism will be described.
[0019]
A general heating resistor type air flow meter converts the voltage as an intake air amount and outputs it when air flows regardless of the flow direction of the air to be measured. That is, the one having no directionality is common.
[0020]
That is, there is a feature that both the air flow rate sucked into the cylinder and the air flow rate blown back from the cylinder for some reason are counted as the intake air amount. This is a so-called error due to the backflow of the intake air.
[0021]
It is a known phenomenon that the reverse flow of the intake air is likely to occur in a high load state with a relatively low rotational speed in the operating state of the internal combustion engine.
[0022]
In this high load state at a relatively low rotational speed, the intake air is pulsated, and as a result, the intake air is sucked in a direction opposite to the intake direction to the cylinder, that is, a so-called reverse flow.
[0023]
FIG. 2 shows what kind of error the output signal of the heating resistor type air flow meter has in this reverse flow state. As shown in FIG. 2, when the engine load increases and the intake pulsation increases, the output of the heating resistor type air flow meter shows an error that greatly jumps to the plus side.
[0024]
In the present invention, the error on the plus side of the heating resistor type air flow meter is reduced by making the delay amount of the delay filter variable.
[0025]
FIG. 3 shows the output characteristics of the heating resistor type air flow meter when a variable delay filter is interposed. If the filter delay amount is made variable in accordance with the instantaneous heating resistor airflow meter output value, a signal having a high wave height is smoothed more greatly and a signal having a low wave height is processed as a signal as it is. As a result, smoothing is performed while lowering the median value of the waveform.
[0026]
Thereby, it turns out that the error on the plus side due to the reverse flow under the intake pulsation can be selectively reduced. This is because the output of the heating resistor type air flow meter under pulsation is in reverse flow, and the output signal in this case is guided in the direction of decreasing the detection value with a delay filter with variable delay amount, and the output of the heating resistor type air flow meter with small pulsation This is because the influence of the delay filter does not appear in the signal, and the change in the detection value due to the delay filter does not appear. FIG. 4 is a part of the control flow in the combustion control of the internal combustion engine using the embodiment of the present invention.
[0027]
Here, the present invention provides a means for accurately converting the output signal of the heating resistor type air flow meter into the intake air flow rate and reflecting it in the combustion control of the internal combustion engine. There is no limitation on methods such as correction of temperature and environmental factors.
[0028]
In FIG. 4, a control unit that realizes combustion control electrically takes in an output signal of the air flow meter. At this time, in the control unit, the A / D converter is usually used for digitization. Next, the digitized electrical signal is converted into an instantaneous air flow rate.
[0029]
Next, the delay amount of the delay filter, which is a feature of the present invention, is searched from the map. Here, in this embodiment, the delay amount of the delay filter is described by map search, but it goes without saying that the delay amount can also be obtained by other means such as a mathematical expression. Further, the air flow rate value obtained from the air flow sensor is filtered using the filter delay amount described above. By such means, it is possible to easily reduce the error of the air flow sensor due to the backflow under pulsation.
[0030]
Up to this point, the method of reducing the plus side error due to the backflow of the intake air amount by making the delay filter delay amount of the present invention variable has been described. However, as another implementation means of the present invention, the filter delay amount is variably set. Air flow sensor due to reverse flow under pulsation by converting the detected flow rate value of the heating resistor type air flow meter into a characteristic having a non-linearity temporarily and smoothing it with a delay filter having at least one delay amount instead Can be reduced.
[0031]
The method will be described below.
[0032]
Although this is different from the case where the delay amount described above is variable, it has the same effect.
[0033]
FIG. 6 shows a change in the output signal when a delay filter is interposed after the characteristic is temporarily converted to a non-linear characteristic. As shown in FIG. 6, the median value of the waveform can be lowered by making the output signal of the heating resistor type air flow meter under pulsation non-linear.
[0034]
This is because when the input waveform such as a sine wave is expressed in a non-linear manner, the higher the wave height, the lower the wave height, and the lower the wave height, the less the compression, so the overall waveform is converted to the smaller one. Therefore, that is, the error on the plus side due to the backflow under the intake pulsation is selectively reduced.
[0035]
This effect becomes more prominent by converting a non-linear line and then interposing a delay filter.
[0036]
As described above, the output signal of the heating resistor type air flow meter has a non-linear output characteristic due to its operating principle, but with this non-linearity as it is, it is not possible to control the median decrease in the appropriate amount of pulsation waveform. .
[0037]
In the present invention, the output signal of the heating resistor type air flow meter is once converted into a flow rate signal, and then converted into an appropriate non-linear output characteristic, thereby performing control to appropriately lower the median value of the waveform.
[0038]
The pulsation signal after lowering the median value is smoothed through a delay filter, and combustion control is performed using this flow value signal.
[0039]
FIG. 6 is a control flow for a routine for calculating the intake air flow rate in the combustion control of the internal combustion engine.
[0040]
The part for digitizing the output signal of the air flow sensor is the same means as in the above-described embodiment. After conversion to the flow rate value, the flow rate value is re-expressed as a uniquely determined non-linear characteristic, and a delay filter is applied to the non-linear data for the actual flow rate value. This result is converted into a flow rate value from the previously determined nonlinear characteristic, and the internal combustion engine is controlled as basic data for combustion control.
[0041]
The embodiment described above is a method for reducing the amount of backflow generated under pulsation only from the output characteristics of the heating resistor type air flow meter. However, as another embodiment of the present invention, the operation state of the internal combustion engine is another means. There is also a method in which a filter having an appropriate delay amount is interposed.
[0042]
In the combustion control of an internal combustion engine, it is a known fact that there are a crank angle sensor 8 for grasping a crank rotation state of the internal combustion engine, a throttle sensor 14 for detecting a throttle opening degree, and the like.
[0043]
The operation state of the internal combustion engine is detected from these sensors, and a filter delay amount suitable for the operation state and an appropriate non-linearization of the output signal are performed. Here, the setting of an appropriate filter delay amount according to the operating state of the internal combustion engine and the appropriate non-linearization of the output signal will be specifically described.
[0044]
In the internal combustion engine, in a situation where the intake air pulsates and the intake air flows backward, it is a known fact that the phenomenon appears when the internal combustion engine is operated at a high load and a relatively low rotational speed. As stated. Therefore, it is possible to easily estimate whether or not the engine is operating at a relatively low speed with a high load by detecting the operating speed and throttle opening of the internal combustion engine. It is known to use these signals to control the operating state of the internal combustion engine.
[0045]
The present invention is characterized in that the smoothing process of the output signal of the heating resistor type air flow meter is made variable or the non-linear process is controlled according to the operating state.
[0046]
FIG. 7 shows the relationship between the throttle opening and the output characteristics of the heating resistor type air flow meter. From this point, when the throttle opening is opened above a certain level, the output characteristics of the air flow meter have a plus error.
[0047]
In the present invention, this characteristic is used to take an error reduction measure for the output characteristic of the air flow sensor by the means described above when the throttle opening is opened above a certain level.
[0048]
FIG. 8 shows a representative example of the output characteristics of the air flow meter when the operating speed of the internal combustion engine and the operating load applied to the internal combustion engine when the throttle opening is fully opened are maximum.
[0049]
From this, it can be seen that the measurement error of the air flow meter is largely present on the low rotation side. This characteristic differs slightly depending on the output characteristics of the internal combustion engine, the total displacement, the intake air introduction method, etc., and not all internal combustion engines are necessarily the same, but they are constant according to the characteristics of the internal combustion engine. When the rotational speed is less than or equal to the value, the above-described error reduction measures for the output characteristics of the air flow sensor can be taken.
[0050]
FIG. 9 shows an example of a control flow for a routine for calculating the intake air flow rate using the operating rotational speed of the internal combustion engine and throttle opening information.
[0051]
The part for digitizing the output signal of the air flow sensor is the same means as in the above-described embodiment. Almost at the same time, the operating speed of the internal combustion engine and the opening of the throttle that limits the intake air amount are obtained from each sensor, and the delay amount of the delay filter that smoothes the output signal of the air flow meter is searched from this information. Based on the delay amount obtained here, the air flow rate obtained by the air flow sensor is smoothed and used for combustion control of the internal combustion engine.
[0052]
Although the embodiment so far has been described using the output signal processing method of the heating resistor type air flow meter in the combustion control of the internal combustion engine using gasoline fuel, the heating resistor type for obtaining the air flow rate of the diesel engine It can also be applied to the processing method of the output signal of the air flow meter.
[0053]
【The invention's effect】
By using the present invention, it is possible to reduce a measurement error during intake pulsation with a small load.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a system configuration of a typical typical internal combustion engine.
FIG. 2 is a characteristic diagram showing a relationship between an engine load of the present invention and an output signal of an air flow meter.
FIG. 3 is a characteristic diagram showing the effect of the variable delay filter of the present invention.
FIG. 4 is a flowchart showing an air flow meter signal processing routine of the present invention.
FIG. 5 is a characteristic diagram showing the effect of flow rate value non-linearization according to the present invention.
FIG. 6 is a flowchart showing an air flow meter signal processing routine of the present invention.
FIG. 7 is a characteristic diagram showing the relationship between the throttle opening and the air flow meter output signal of the present invention.
FIG. 8 is a characteristic diagram showing the relationship between the operating speed of the internal combustion engine of the present invention and an air flow meter output signal.
FIG. 9 is a flowchart showing an air flow meter signal processing routine of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Combustion control unit, 2 ... Heating resistor type air flow meter, 3 ... Throttle chamber, 4 ... Injector, 5 ... Oxygen sensor, 6 ... Spark plug, 7 ... Ignition coil, 8 ... Rotation sensor, 9 ... Air cleaner, 10 ... Intake manifold, 11 ... intake valve, 12 ... crank, 13 ... exhaust valve, 14 ... throttle sensor.

Claims (3)

Converting a heating resistor airflow meter signal into a flow rate value;
A variable filter amount search step for increasing the delay amount at a high wave height of the instantaneous flow rate value and decreasing the delay amount at a low wave height of the instantaneous flow rate value ;
A signal processing method for a heating resistor type air flow meter for an internal combustion engine, comprising: a flow value filtering step for delaying the flow value based on the delay amount. In claim 1,
A signal processing method for a heating resistor type air flow meter, wherein the median value of the flow rate value after the flow rate value filtering step is smaller than the median value of the flow rate value before the flow rate value filtering step during intake pulsation. In claim 1,
Detect the operating speed and throttle opening of the internal combustion engine,
A signal processing method for a heating resistor type air flow meter, wherein a delay amount in the variable filter amount search step is searched based on detected information.

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