JP2011052964A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that a detection error is large, a detection delay is caused, and a flow rate detection error is generated in a conventional method in which, when operating an air flow rate for each prescribed time from a frequency output signal of an air flowmeter, the latest one period of the signal is converted into a flow rate for each prescribed time to obtain a detection flow rate. <P>SOLUTION: A control device of an internal combustion engine reduces response delay by performing differential correction of a detection flow rate in a transient region. Further, rather than calculating a flow rate after calculating an average period to perform the conversion into the flow rate, a signal of the air flowmeter is converted into the flow rate for each period to perform average processing by the unit of the flow rate. Accordingly, the flow rate detection error due to nonlinearity between the period and flow rate is reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a waveform measurement method and a flow rate calculation method for an electronic device that measures a waveform output from a frequency output type air flow meter and calculates the flow rate.

  In the control device for an internal combustion engine, an air flow meter is attached to the intake pipe of the internal combustion engine in order to measure the air flow rate taken in by the internal combustion engine, and the signal detected by the air flow meter is the air flow rate calculation device. The fuel injection amount is calculated based on this value.

  In recent years, fuel efficiency regulations and exhaust gas regulations have been strengthened, and high accuracy in calculation of fuel injection amount of internal combustion engine and calculation of intake air flow rate of internal combustion engine is an important technical issue. In addition, reduction of errors occurring at the interface between the air flow meter and the air flow calculation device is also an important issue.

Japanese Patent Laid-Open No. 02-129522

  When calculating the air flow rate at a predetermined time from the frequency output signal of the air flow meter, conventionally, one cycle of the latest signal of the signal is converted into a flow rate at a predetermined time to obtain a detected flow rate. However, in the conventional method, if the vibration period of the flow rate is a constant multiple of the flow rate measurement period during the intake pulsation where the air flow rate vibrates, the measured flow rate cannot be reproduced, so the measurement error increases. A phenomenon called aliasing occurs. On the other hand, in Japanese Patent Application Laid-Open No. 02-129522, the average period of all waveforms within a predetermined time interval is calculated for the signal, and converted to a flow rate based on the average period, thereby reducing the influence of the aliasing. Reduced. However, the method of obtaining the average period and converting it to the flow rate is equivalent to performing the moving average process, and a detection delay occurs. Therefore, in the transient region where the air flow rate change is large, the response delay increases and the detection error increases. There is a problem of becoming. If the detection error of the air flow rate becomes large during the intake transient, the detected air flow rate becomes smaller than the air flow rate when there is no error, so the fuel injection amount calculated based on the detected air flow rate also becomes small. Here, the fuel injection amount needs to be injected so as to be a constant value called a theoretical mixing ratio with respect to the intake air amount. If the fuel injection amount and the intake air flow rate deviate from the theoretical mixing ratio, harmful components such as HC, CO, and NOx are discharged from the exhaust gas of the internal combustion engine, which causes a problem.

  In addition, when the flow rate is calculated from the average period of the signal within a predetermined time interval, the average value and the average period of the flow rate during intake pulsation due to the nonlinearity of the relationship between the cycle and the flow rate, which is the output characteristic of the thermal air flow meter Therefore, there is a problem that a flow rate detection error occurs.

  The present invention has been made to solve the above-described problem, and has an object to reduce a flow rate detection error due to a nonlinear relationship between a response delay in a transient region, a cycle, and a flow rate.

By calculating the average period of all waveforms within a specified time interval for the frequency output signal of the air flow meter, and converting it to a flow rate based on the average period, flow detection errors due to the effects of aliasing are reduced, and transients Response delay is reduced by performing differential correction in the region.
Also, instead of calculating the flow rate after calculating the average cycle, the flow rate is calculated by converting the air flow meter signal into a flow rate for each cycle and performing the averaging process in units of flow rate. Reduces the flow detection error due to.

  According to the present invention, since the flow rate is obtained based on the average value of all output waveforms within a predetermined time interval, the flow rate detection error due to aliasing can be reduced even during intake pulsation at any frequency. Since the intake pulsation is a phenomenon caused by the vertical movement of the piston and the resonance of the intake pipe, the intake pipe design for avoiding a specific frequency becomes unnecessary because of concern about aliasing. At the same time, it means that the air flow rate calculation period can be freely set separately from the intake pulsation period.

  In addition, according to the present invention, it is possible to reduce the flow rate detection delay that occurs during intake transients in order to obtain the flow rate based on the average value of all output waveforms within the predetermined time interval. Accordingly, it is possible to calculate an accurate intake air flow rate of the internal combustion engine even during an intake transient.

  Further, according to the present invention, electrical noise or the like acts on the signal line connecting the air flow meter and the air flow rate calculation device, and a cycle that is temporarily different from the cycle corresponding to the detected flow rate is input to the air flow rate calculation device. Even in this case, since the flow rate is calculated using a plurality of waveforms within a predetermined time interval, the influence of an erroneous cycle is reduced. Therefore, it is possible to avoid applying response delay correction to a flow rate value that is greatly different from the flow rate detected due to the influence of noise.

  According to the invention, since the frequency output waveform of the air flow meter changes in accordance with the detected flow rate, the frequency output waveform input within a predetermined time interval according to the detected flow rate of the air flow meter. The number of waveforms changes. Here, the method of calculating the flow rate using a plurality of waveforms according to the present invention is equivalent to performing the moving average process, and changing the number of waveforms input within a predetermined time interval means that the average process of the moving average process is performed. This means that the number of samples used in the process changes. However, at the same time, a change in the period of the frequency output waveform of the air flow meter changes the flow rate detection sampling period, that is, the sampling frequency of the moving average process changes. Therefore, according to the detected flow rate, the number of frequency output waveforms input within a predetermined time interval and the sampling period change at the same time, that is, the sampling number and sampling frequency of the moving average processing change at the same time. The change in frequency characteristics is small. This means that the detection delay amount during intake transient hardly changes depending on the flow rate range to be detected. Therefore, even during intake transients in any flow rate range, according to the present invention, an accurate response delay can be obtained by using a value obtained by multiplying a detected flow rate change value by a constant or a table converted value as a flow rate correction value. It is possible to make corrections.

  Further, according to the present invention, even during intake pulsation in a region where the relationship between the flow rate and the cycle shows a strong non-linearity, all output waveforms within a predetermined time interval are converted into a flow rate for each waveform, and the unit of flow rate. Since the average flow rate is calculated by averaging, the flow rate detection error due to the nonlinearity can be reduced. Therefore, it is possible to reduce the average flow rate detection error even at the time of intake pulsation in a region where the relationship between the flow rate and the period shows a strong nonlinearity.

  Further, according to the present invention, it is possible to apply the response delay correction only when there is a change in the air flow rate that coincides with the change in the intake transient even during the intake transient during the intake pulsation, and in a region where the intake pulsation is large Since it is possible not to apply the response delay correction, it is possible to prevent the response delay correction from having an adverse effect. Therefore, it is possible not to deteriorate the calculation accuracy of the air flow rate even at the time of intake transient during intake pulsation.

  Since the amount of fuel injected in the internal combustion engine is calculated based on the detected air flow rate, the adoption of the present invention brings the air flow rate sucked into the internal combustion engine and the combustion injection amount close to the optimum mixing ratio. Therefore, harmful components such as HC, CO, NOx contained in the exhaust gas of the internal combustion engine can be reduced.

The entire engine system. Explanation of the control unit. Explanation of thermal airflow sensor. Explanation of the frequency output calculation unit of the air flow sensor. Output waveform of frequency output type air flow sensor. The relationship between the flow rate and frequency or cycle of the frequency output type air flow sensor. Period detection method for airflow sensor output waveform. A method for calculating an average period of an output waveform of an airflow sensor within a predetermined time interval. Mechanism in which flow rate detection error occurs due to nonlinearity of flow rate and period during intake pulsation. A method for calculating an average flow rate of an airflow sensor output waveform within a predetermined time interval. A mechanism that causes a detection delay from the average process during intake transients. Delay correction applied only during intake transients. Explanation 1 of the delay correction value. Explanation 2 of the delay correction value. Delay correction method during intake pulsation.

Embodiments of the present invention will be described below with reference to the drawings.
First, the outline of the operation of the internal combustion engine and the fuel injection amount control using the air flow sensor signal which is the air flow rate detection device, which are the premise in the embodiment of the present invention, will be described.
FIG. 1 shows a so-called MPI (multi-cylinder fuel injection) type four-cylinder internal combustion engine. Hereinafter, an MPI type four-cylinder internal combustion engine will be described as an example of the present invention. However, the embodiment of the present invention is not necessarily limited to the MPI type four-cylinder internal combustion engine, and a frequency is used as an output value. This includes all internal combustion engines with a conventional air flow meter.

The intake air flow rate of the internal combustion engine is measured by a hot-wire air flow sensor 2 provided at the outlet of the air cleaner 1. The intake air enters the collector 6 through the intake pipe 3 connected to the air cleaner 1 and the throttle body 5 having the throttle valve 4 for adjusting the intake air flow rate. Thereafter, the air is distributed to the intake branch pipe 7 that forms a part of the intake pipe 3, passes through the intake valve 8, and is sucked into the cylinder 9.
Further, the fuel is sucked and pressurized from the fuel tank 10 by the fuel pump 11, adjusted to a constant pressure by the pressure regulator 12, and injected from the injector 13 provided in the intake pipe 3 into the intake branch pipe 7. The
In the cylinder 9, the spark plug 14 ignites a gas in which air and fuel are mixed in the intake branch pipe 7 to burn the fuel. The exhaust gas after burning in the cylinder of each cylinder passes through the exhaust pipe 16, is purified by the catalyst 17, and is then discharged out of the internal combustion engine.

As shown in FIG. 2, the control unit 18 includes a power supply IC 40, a RESET signal 41, and an LSI 42, and a RESET signal 41 controlled by the power supply IC 40 is connected to the RESET terminal of the LSI 42. Yes.
In the control unit 18, an output value of each sensor installed in the internal combustion engine and an output value of a sensor for detecting operation information of a driver of the vehicle in which the internal combustion engine is installed are output by an A / D converter built in the LSI 42. Each actuator is controlled by converting it into a digital value and performing an operation, and outputting the operation result as a control signal.
As a signal to be input to the control unit 18, a hot-wire airflow sensor 2, a crank angle sensor 19, an air-fuel ratio sensor 20, an opening sensor of the throttle valve 4, and power from the battery 23 via the starter switch 22, accelerator opening There is a signal from the sensor 30.
A control signal output from the control unit 18 is output to the power transistor 24 that is an ignition switch of the injector 13, the fuel pump 11, and the spark plug 14.

The hot wire type air flow sensor 2 will be described.
The hot-wire airflow sensor 2 installed in the intake pipe is provided with a bypass passage, and has a heating resistor 50 and a temperature-sensitive resistor 51 therein. As shown in FIG. 3, a feedback circuit 53 is configured by a bridge circuit, and the temperature difference between the heating resistor 50 and the temperature-sensitive resistor 51 is controlled to be always constant.

When the amount of intake air is large, the heat generating resistor 50 is cooled by heat dissipation, and the current flowing through the heat generating resistor 50 increases so that the temperature difference between the heat generating resistor 50 and the temperature sensitive resistor 51 becomes constant. 52 becomes larger.
Conversely, when the amount of intake air is small, the cooling effect of the heat generating resistor 50 due to heat radiation is reduced, the current flowing through the heat generating resistor 50 is reduced, and the output voltage 52 is reduced.
Further, the thermal airflow sensor includes an LSI 58 therein, and converts the output voltage 52 of the bridge circuit 53 into a digital value by an A / D converter in the LSI 58. The air flow rate detection value converted into a digital value is subjected to a flow rate correction calculation 55, subjected to frequency conversion 56 with a predetermined clock, and output as a sensor as a frequency output value 57.

Here, details of the frequency converter 56 will be described next. The detected air flow rate value in the hot-wire air flow sensor 2 is input to the frequency conversion unit 56 operating at a predetermined clock as a flow rate equivalent value as shown in FIG. In the frequency converter, the flow rate equivalent value is subtracted from the previous value of B every predetermined clock. When the value A after subtraction is negative, the value of B is reset to the value of DIG_RESET 61, and when it is positive, the value of B becomes the value of A as it is. Depending on the value of B, the voltage value that is finally output changes. When the value of B is larger than the value of DIG_RESET / 2, the high level voltage 63, and conversely, when the value of B is smaller than DIG_RESET / 2, the low level voltage 64 is output as a sensor as a frequency output 57.
As a result, the frequency output waveform of the hot-wire airflow sensor 2 becomes a waveform as shown in FIG. 5 in which the high level voltage 63 and the low level voltage 64 are alternately output. From the operating principle of the frequency converter 56, as shown in FIG. 6, when the air flow rate detected by the air flow sensor is low, a low-frequency rectangular wave, and conversely, when the air flow rate is high, a high-frequency rectangular wave. Is output. Further, in the thermal air flow sensor, the relationship between the detected flow rate and the frequency or cycle is nonlinear due to the operation principle.

  Next, the control unit 18 that detects the output signal of the hot-wire airflow sensor 2 as a cycle and converts it into a flow rate will be described. As shown in FIG. 7, the output signal of the hot-wire airflow sensor 2 is detected as a cycle by using the timer 80 in the control unit 18. Next, an embodiment in which the airflow sensor signal is detected as a cycle will be described. First, the timer 80 of the control unit 18 that counts up the counter with a predetermined clock detects a rising edge that changes from the low level voltage 64 to the high level voltage 63 of the output signal of the airflow sensor. The timer 80 resets the counter value after detecting the rising edge, and counts up the timer with a predetermined clock until the next rising edge is detected. At the same time, the timer 80 detects the counter value of the timer at each rising edge of the thermal airflow sensor output signal, and stores the counter value in a RAM provided in the control unit 18. Therefore, it is possible to calculate the time of one cycle of the output signal of the hot-wire airflow sensor 2 by multiplying the counter value of the timer stored in the RAM at the time of detecting the rising edge before and after the continuous.

  Further, as shown in FIG. 8, the period of all output signals of the hot-wire airflow sensor 2 detected within the predetermined time interval is detected by using all the counter values of the timer stored in the RAM within the predetermined time interval. Therefore, it is possible to calculate the average period Tave90 of all the output signals of the airflow sensor detected within a predetermined time interval by averaging all the periods. The flow rate of the average period Tave90 obtained at the end is converted into a detected flow rate.

  However, since the relationship between the flow rate and the cycle of the hot-wire air flow sensor 2 is non-linear, the following problems occur in the intake pulsation state. Before describing the problem, first, the intake pulsation state will be explained. The intake pulsation state is a resonance called pulsation due to the resonance of the air pressure vibration generated by the vertical movement of the piston and the vibration due to the natural frequency of the intake pipe in the engine. This is a state where a phenomenon occurs. At this time, as shown in FIG. 9, there is a problem that a deviation due to non-linearity of the flow rate characteristic occurs between the value converted from the average period of the output waveform of the hot-wire air flow sensor 2 to the flow rate and the actual average flow rate.

  Therefore, as shown in FIG. 10, each cycle of all output signals of the hot-wire airflow sensor 2 detected within a predetermined time interval is converted into a flow rate, and then the flow rate is averaged to detect within a predetermined time interval. It is possible to calculate an average flow rate Qave91 of all output signals of the airflow sensor. By this method, it is possible to reduce the flow rate detection error due to the nonlinearity of the flow rate and the cycle.

  However, since the average process described above is a process equivalent to the moving average process, the air flow rate Q obtained by this process has a delay with respect to the true air flow rate. As shown in FIG. 11, the average period obtained by the averaging process is delayed more than the period of every one cycle by 0.5 cycle of the air flow rate calculation period, especially at the intake transient when the change of the air flow rate is large. Therefore, the flow rate detection error due to the detection delay becomes large during the intake air transient. If the detection error of the air flow rate becomes large during the intake transient, the detected air flow rate becomes smaller than the air flow rate when there is no error, so the fuel injection amount calculated based on the detected air flow rate also becomes small.

  Here, the fuel injection amount needs to be injected so as to be a constant value called a theoretical mixing ratio with respect to the intake air amount. If the fuel injection amount and the intake air flow rate deviate from the theoretical mixing ratio, harmful components such as HC, CO, and NOx are discharged from the exhaust gas of the internal combustion engine, which causes a problem. Therefore, an embodiment for reducing a flow rate detection error due to a detection delay even during an intake transient will be described below.

  First, the amount of change in the air flow rate that passes through the throttle body 5 is used as a transient flow rate region discriminating means. The flow rate of air passing through the throttle body 5 is calculated from the engine speed obtained from the total flow area of the throttle body 5 calculated from the opening of the throttle valve 4 and the output value of the crank angle sensor 19. When the amount of change in the air flow rate passing through the throttle body 5 is greater than a certain value, the detected air flow rate is assumed to be in a transient region, and as shown in FIG. By performing delay correction on the air flow rate 110 obtained by the average processing calculation and setting the flow rate 111 after the delay correction as the intake air flow rate, the flow rate detection error at the time of intake transient is reduced.

  Here, the delay correction is calculated as follows. In the present invention, as shown in FIG. 13, the delay correction value is calculated based on the change amount ΔQ120 of the air flow rate obtained from the signal of the hot-wire airflow sensor 2. That is, the delay correction value is a value QhoseiK121 obtained by multiplying a constant Δ by a difference ΔQ120 between the air flow rate Q110 obtained from the signal of the hot-wire airflow sensor 2 calculated every predetermined time interval and the previous value of the air flow rate. The sum of the correction value 121 and the air flow rate Q110 obtained from the signal of the hot-wire airflow sensor 2 is used as a value used for the fuel injection amount calculation as the air flow rate QkatoK122 after delay correction. By this calculation, the response delay caused by the averaging process is reduced and the flow rate detection error is reduced, so that the fuel injection amount becomes a value that approaches the theoretical mixing ratio with respect to the intake air flow rate of the internal combustion engine.

  However, when the delay correction value is a value QhoseiK121 obtained by multiplying the difference ΔQ120 by the constant K, the following problem occurs. The method of calculating the flow rate using a plurality of waveforms according to the present invention corresponds to applying a low-pass filter by moving average processing as described above. Therefore, the gain after the low-pass filter decreases as the frequency of the detected air flow rate increases. That is, the greater the change in air flow rate per unit time during the intake transient, the greater the detection delay caused by calculating the flow rate using a plurality of waveforms. Therefore, when the change in the air amount per unit time during the intake air transition is different, a plurality of waveforms are used for the difference ΔQ120 between the air flow rate Q110 obtained from the signal of the hot-wire air flow sensor 2 and the previous value of the same air flow rate. The relationship between the delay correction amounts for reducing the detection delay caused by the flow rate calculation is nonlinear, and if the delay correction value is a value QhoseiK121 obtained by multiplying the difference ΔQ120 by a constant K, highly accurate delay correction is performed. I can't.

  According to the present invention, as shown in FIG. 14, the difference ΔQ120 between the air flow rate Q110 obtained from the signal of the hot-wire airflow sensor 2 that calculates the delay correction value at predetermined time intervals and the previous value of the same air flow rate is obtained. The table converted value is QhoseiT123. The sum of the correction value 123 and the air flow rate Q110 obtained from the signal of the hot-wire air flow sensor 2 is used as the value used for the fuel injection amount calculation as the air flow rate QkatoT124 after delay correction. Even if the delay correction amount is nonlinear with respect to the difference between the air flow rate Q110 obtained from the signal of the hot-wire airflow sensor 2 and the previous value of the same airflow rate by this calculation process, the delay correction is highly accurate. Can be performed.

  So far, the delay correction for the flow rate obtained by averaging the signal of the hot-wire airflow sensor 2 has been described. However, there is an exceptional engine state where the effect of the delay correction at the time of intake transient cannot be obtained so much To do. The engine state is an intake pulsation state. When an intake transient occurs in the intake pulsation state, a flow rate change occurs opposite to the intake transient flow rate change due to the pulsation with respect to the flow rate that greatly changes during the intake transient. If the delay correction is applied to this waveform, the delay correction is also applied to the flow rate that changes in the opposite direction to the flow rate change of the intake transient, which has an adverse effect. Therefore, when an intake transient occurs in the intake pulsation state, as shown in FIG. 15, the flow rate change of the air flow rate Q110 obtained from the sign 130 of the flow rate change of the intake transient and the signal of the hot-wire airflow sensor 2 The delay correction is performed only when the sign 131 of ΔQ matches. That is, the delay correction is performed only when the sign 130 of the air flow rate change amount passing through the throttle body 5 and the sign 131 of the air flow rate change obtained from the signal of the hot-wire air flow sensor 2 match. By this calculation, an appropriate delay correction can be performed even during an intake transient in the intake pulsation state.

  However, in the case where the fluctuation of the air flow rate due to the intake pulsation is larger than the flow rate change during the intake transient, the method cannot perform appropriate delay correction. Therefore, the delay correction is not performed in a specific engine state where the intake pulsation state becomes large. That is, delay correction is not applied when the intake pulsation state is large, at a specific engine speed, and at the throttle valve opening of the throttle body 5. This prevents the delay correction from having an adverse effect.

  In an engine employing a thermal air flow sensor with frequency output, the present invention is very effective and likely to be used.

DESCRIPTION OF SYMBOLS 1 Air cleaner 2 Hot wire type air flow sensor 3 Intake pipe 4 Throttle valve (throttle)
5 Throttle body 6 Collector 7 Intake branch pipe 8 Intake valve 9 Cylinder 10 Fuel tank 11 Fuel pump 12 Pressure regulator 13 Fuel injection device (injector)
14 Spark plug 16 Exhaust pipe 17 Catalyst 18 Control unit 19 Crank angle sensor 20 Air-fuel ratio sensor 21 Ignition switch 22 Starter switch 24 Power transistor 30 Accelerator opening sensor 40 Power supply IC
42 LSI
50 Heating Resistor 51 Temperature Sensitive Resistor 52 Air Flow Sensor Feedback Circuit Output Voltage 53 Air Flow Sensor Feedback Circuit 54 Air Flow Sensor A / D Converter 55 Air Flow Sensor Flow Rate Correction Logic 56 Air Flow Sensor Frequency Conversion Logic 57 Air Flow Sensor Frequency output signal 58 Airflow sensor LSI
61 Frequency conversion logic internal reset signal 63 High frequency voltage of frequency output signal 64 Low level voltage of frequency output signal 80 Timer 90 in control unit Average period of frequency output waveform of air flow sensor 91 Average flow rate of frequency output waveform of air flow sensor 110 Detected flow rate Q of air flow sensor after average processing
111 Flow rate 120 after delay correction Difference ΔQ from previous value of air flow sensor detected flow rate Q after average processing
121 Delay correction value 122 obtained by multiplying ΔQ by a constant 122 Delay correction value 124 obtained by performing a delay correction using a delay correction value obtained by multiplying a constant by ΔQ Delay correction value 124 obtained by table conversion of ΔQ Air flow rate 130 Sign of flow change at the time of transition 131 Sign of ΔQ

Claims (11)

In an air flow rate calculation device having an air flow meter that outputs a frequency signal corresponding to a measured value of an air flow rate, and a means for detecting the frequency output signal output from the air flow meter as a cycle and converting the cycle to an air flow rate ,
Means for calculating an average period of all output signals of the air flow meter detected within a predetermined time interval;
An air flow rate calculation device, wherein a correction is applied to a value obtained by converting an average period of all the output signals into a flow rate in a transient region where a change in air flow rate is large.   2. The air flow rate calculation apparatus according to claim 1, wherein the correction is a value obtained by multiplying a difference between a value obtained by converting the average period into a flow rate and a previous value by a predetermined constant.   In Claim 1, The said correction | amendment is the value which converted the difference with the last time value of the value which converted the said average period into the flow volume with the table, The air flow rate calculating apparatus characterized by the above-mentioned.   4. The air flow rate calculation device according to claim 1, wherein in the transient region, the correction is performed only when the sign of the transient change and the sign of the difference between the previous values match.   4. An air flow rate calculation device according to claim 1, wherein said correction is not applied in a specific region of engine speed and throttle opening. In an air flow rate calculation device having an air flow meter that outputs a frequency signal corresponding to a measured value of an air flow rate, and a means for detecting the frequency output signal output from the air flow meter as a cycle and converting the cycle to an air flow rate ,
An air flow rate calculation device that calculates an average flow rate from a total flow rate value after converting all the outputs of the air flow meter detected within a predetermined time interval into a flow rate every cycle. In an air flow rate calculation device having an air flow meter that outputs a frequency signal corresponding to a measured value of an air flow rate, and a means for detecting the frequency output signal output from the air flow meter as a cycle and converting the cycle to an air flow rate ,
A means for calculating an average flow rate from a total flow value after converting all the outputs of the air flow meter detected within a predetermined time interval into a flow rate for each cycle;
An air flow rate calculation device, wherein the average flow rate value is corrected in a transient region where the air flow rate change is large.   8. The air flow rate calculation device according to claim 7, wherein the correction is a value obtained by multiplying a difference from a previous value of a value obtained by converting the average period into a flow rate by a predetermined constant.   8. The air flow rate calculation device according to claim 7, wherein the correction is a value obtained by converting a difference between a value obtained by converting the average period into a flow rate and a previous value using a table.   10. The air flow rate calculation device according to claim 6, wherein in the transient region, the correction is performed only when the sign of the transient change and the sign of the difference between the previous values match.   10. The air flow rate calculation device according to claim 6, wherein the correction is not performed in a specific region of the engine speed and the throttle opening.

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