JP4050221B2 - Cylinder intake air amount calculation device - Google Patents

Description

  The present invention relates to a technique for calculating the amount of air taken into a cylinder of an internal combustion engine (engine) used in an automobile or the like.

There is an air flow sensor (AFS) as a device for detecting the intake air amount of an engine. Patent Document 1 describes that the intake air amount to the cylinder is calculated from the intake air amount detected from the air flow meter, the change amount of the intake pressure detected from the intake pressure sensor, and the intake air temperature. .
JP 2000-16113 A

  In the intake air amount calculation method using the outputs of the air flow sensor and the intake pressure sensor, in order to reduce the pulsation component generated in the output of the air flow sensor and the output of the intake pressure sensor, a moving average of the sample values of these outputs for a predetermined period It has been proposed to take. The inventor of the present application reduces the pulsation component when the moving average target period is lengthened in order to reduce the pulsation component, but the intake air amount calculated in a transient state such as when the automobile accelerates is reduced. We observed a delay from the actual value. For example, when the automobile is in an acceleration state, the calculated intake air amount indicates a value lower than the actual value. The electronic control unit of the engine performs control to perform fuel injection according to the target air-fuel ratio based on this low value. As a result, the air-fuel ratio becomes leaner than the target air-fuel ratio and affects acceleration performance. become.

  Accordingly, an object of the present invention is to provide a method for calculating a cylinder intake air amount that reduces such problems.

    In order to solve the above problems, an apparatus for calculating a cylinder intake air amount according to the present invention includes an intake air amount sensor for detecting an intake air amount provided in an intake pipe of an internal combustion engine, and an intake pipe intake. And an intake pressure sensor for detecting the atmospheric pressure. The apparatus of the present invention further includes an air amount averaging means for sampling the output of the intake air amount sensor to calculate an average intake amount, and an intake pressure average for calculating the average intake pressure by sampling the output of the intake pressure sensor. Means. The device of the present invention further includes a correction amount calculating means for calculating a correction amount for correcting the average intake air amount based on the fluctuation of the average intake pressure, and the correction amount calculating means is for operating the internal combustion engine. The correction amount is calculated using a coefficient corresponding to the state.

  According to the present invention, the average intake air amount is corrected based on the fluctuations in the average intake pressure, and the correction amount is calculated using a coefficient corresponding to the engine operating state. The amount of intake air can be calculated.

  In one form (Claim 2), the coefficient is a value corresponding to a change in the average intake pressure, and in another form (Claim 3), the coefficient is a current value of the average intake pressure. It is determined according to the difference from the previous value.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of the entire engine system. The intake air passes through the intake pipe 11 and is supplied to a cylinder (hereinafter referred to as a cylinder) 10 according to the opening of the throttle 15. The gas burned in the cylinder 10 passes through the exhaust pipe 23 and is exhausted into the atmosphere.

  The intake pipe near the cylinder 10 is provided with an injector 21 for injecting fuel. In the in-cylinder direct injection engine, the injector 21 is provided so that the nozzle is located in the cylinder. An air flow sensor 13 for detecting the air flow rate is provided upstream of the throttle 15. The air flow sensor is an air flow meter, and a vane air flow sensor, a Karman vortex air flow sensor, and a hot wire air flow sensor are known. The present invention can be used with any of these airflow sensors.

  Although not shown in the figure, the crankshaft of the engine is provided with a crank angle sensor that outputs a reference angle signal for each fixed angle according to the rotation of the engine. In this embodiment, a crank pulse is generated every 30 degrees of rotation of the crankshaft, and the output of the air flow sensor is sampled at the cycle of the crank pulse.

  Electronic control unit (Electronic Control Unit) composed of a microcomputer that outputs the crank angle sensor, the water temperature sensor that detects the engine water temperature, the output of the airflow sensor, the air-fuel ratio sensor, and other sensors provided in each part of the engine ) Input to 30 input interfaces 31. The input interface 31 processes the input signal and passes the output to the operating state determination unit 37. The driving state determination unit determines the driving state of the vehicle from the input signal and passes the output to the control calculation unit 39. The control calculation unit 39 performs calculation for performing air-fuel ratio control according to the operating state, and outputs a signal for driving the injector 21, spark plug, and other components.

  The intake air amount necessary for controlling the fuel injection amount is calculated based on the measurement output of the air flow rate by the air flow sensor 13. The output of the airflow sensor 13 is subjected to waveform processing at the input interface 31 of the ECU 30, sampled at a crank pulse period, converted into a digital signal by an analog / digital converter, and sent to an intake air amount (GAIRTH) calculation unit 35.

  It is known that the output of the airflow sensor 13 includes a pulsation having a period T as an intake process (TDC) of the engine. The air amount calculation unit 35 includes a moving average digital filter that processes a sample value sent from the input interface 31 and outputs a value obtained by removing the pulsation frequency component.

  Next, referring to FIG. 2, it is known that when the throttle opening greatly changes, an overshoot occurs in the intake air amount GAIRTH (indicated by Gair-th in FIG. 2) based on the air amount measurement by the air flow sensor. This phenomenon is known to occur due to a change in the amount of air GB charged in the intake manifold 19 (FIG. 1) downstream of the throttle. Here, the air amount Gair-afs (g / sec) calculated from the air flow sensor output is converted into an intake air amount GAIRTH (g / TDC) per cylinder. For example, with 4 cylinders, GAIRTH = Gair-afs * 60 / (NE * 2), and with 6 cylinders, GAIRTH = Gair-afs * 60 / (NE * 3).

  Further, it is known that the overflow due to the air amount filled with the manifold is corrected by the following equation, and the air amount Gair-cyl sucked into the cylinder 10 is calculated.

Formula 1
GAIRCYL = GAIRTH-ΔPB ・ V / (R ・ T)

  Here, ΔPB is the pressure of the intake pipe detected by the pressure sensor 17 (FIG. 1) provided in the intake pipe, V is the volume of the manifold, R is a gas constant, and T is the intake air temperature (absolute temperature).

  Referring to FIG. 1, the output of the intake pressure sensor 17 disposed near the intake pipe (intake manifold) is sent to the input interface 31 of the ECU 30, sampled at a crank pulse period, converted into a digital value, and converted into a PBAVE calculation unit 33. Sent to. Similar to the GAIRTH calculation unit 35, the PBAVE calculation unit 33 includes a moving average digital filter, and calculates a moving average value of the intake pressure.

  FIG. 3A shows sampling (81) in the crank pulse period (30 degrees) of the intake air amount and the intake pressure in a four-cylinder engine, and TDC periods (180 degrees = 6 in the PBAVE calculation unit 33 and GAIRTH calculation unit 35). The timing relationship of intake pressure average value and intake air amount average value calculation (83) in the crank pulse period) is shown. FIG. 3B shows a timing for calculating the average value of the intake air amount and the average value of the intake pressure by calculating the moving average in the 4TDC section for the average value of the TDC period obtained at the timing shown in FIG. ). That is, in FIG. 3B, the average value is calculated by the moving average of the 4TDC section and the 24 crank pulse section.

  In the average value calculation at the timing shown in FIG. 3A, pulsation of 4 TDC cycle occurs in the output. However, when the moving average section is made long, for example, at the timing shown in FIG. 3B, this pulsation component may not appear. Observed. However, when such a long moving average section is employed, a problem occurs in the transient characteristics of the calculated cylinder intake air amount GAIRCYL. That is, in a state where a relatively large change occurs in the intake pressure and the intake air amount, such as when the driving state of the vehicle is in an acceleration state, the calculated cylinder intake air amount GAIRCYL is delayed from the actual cylinder intake air amount value. It was observed. For example, when in the acceleration state, the calculated value of GAIRCYL is smaller than the actual cylinder intake air amount.

  The inventor of the present application calculates the GAIRINVO represented by the following equation 2 by multiplying the two items on the right side of the following equation 1 by the correction coefficient KINVO in the range of 0 to 1, and the cylinder intake air amount GAIRCYL is calculated by the equation 3. It was recognized that this phenomenon can be reduced by calculating.

Formula 2
GAIRINVO = ΔPB ・ V / (R ・ T) × KINVO
Formula 3
GAIRCYL = GAIRTH − GAIRINVO

  FIG. 4 shows a flow of a routine program for calculating GAIRINVO. This routine program is executed with a crank pulse period. In this embodiment, the intake pressure average value PBAVE is obtained according to the method of FIG. 3B (step S101). The intake pressure average value PBAVE (85) obtained by the method of FIG. 3B is the moving average value of the intake air pressure in the 24 crank pulse section as described above. A difference ΔPBAVE between the current value of PBAVE and the previous value is obtained (S103).

  Before or after or in parallel with this processing, the intake air amount average value GAIRAVE based on the airflow sensor output is obtained by the method of FIG. This average value is also an average value in the 24 crank pulse section. The amount of change GAIRVS is obtained by performing smoothing calculation of the amount of change in GAIRAVE (S107). This annealing calculation is performed using, for example, the following equation.

Formula 4
GAIRVS (n) = dgairave_temp × c + GAIRVS (n-1) × (1-c)

  Here, c is a smoothing coefficient, 0 <c <1, and a typical value is 0.2 to 0.3. dgariave_temp is a temporary variable and is the difference between the current value of GAIRAVE and the previous value.

  If GAIRVS is greater than or equal to the lower limit value (S109) and less than or equal to the upper limit value (S111), the process proceeds to step S113 to check whether the throttle opening THA is greater than or equal to the throttle opening THIDLE during idling. When THA is less than THIDLE and the vehicle speed VP is below a predetermined value (S115), the value of KINVO is set to 0 (S117). Therefore, the correction term GAIRINVO based on the intake pressure sensor output calculated by Expression 2 is 0 (S121).

  When GAIRVS is less than the lower limit (S109) or exceeds the upper limit (S111), the value of KINVO is obtained from the table shown in FIG. 5 prepared in advance according to the value of ΔPBAVE obtained in step S103 (S119). . The table in FIG. 5 is set to take a larger value as the absolute value of ΔPBAVE is larger. In FIG. 5, when the absolute value of ΔPBAVE is small, the setting of KINVO to be 0 corresponds to entering step S117 in the above-described process. With respect to FIG. 5, alternatively, when the absolute value of ΔPBAVE is small, KINVO may be set to a small value such as 0.3. A line parallel to the horizontal axis near the value 0.3 on the vertical axis in FIG. 5 indicates such an alternative setting. When the throttle opening is equal to or greater than the throttle opening at idling in step S113, and also when the vehicle speed VP exceeds a predetermined value in step S115, the process proceeds to step S119, and KINVO is set as described above.

  Using KINVO set in this way, GAIRINVO is calculated by Equation 2 (S121). Using this GAIRINVO, the cylinder intake air amount GAIRCYL is calculated by Equation 3. Using this GAIRCYL, the engine electronic control unit 30 (FIG. 1) calculates the fuel injection time for operating the injector and sends a drive signal to the injector.

  Although the present invention has been described with respect to specific embodiments, the present invention is not limited to such embodiments.

The functional block diagram which shows the whole structure of one Example of this invention. The wave form diagram which shows the relationship between the intake air amount calculated according to an airflow sensor output, and the cylinder intake air amount which should be. The timing diagram which shows the method of calculating | requiring the sample value of intake air amount and intake pressure based on an airflow sensor output and an intake pressure sensor output, and calculating | requiring the average value thereof. The figure which shows the flow of the routine program which calculates | requires the correction | amendment term of the intake air amount in one Example of this invention. The figure which shows the table referred in step S119 of the flow of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 13 Air flow sensor 17 Intake pressure sensor 33 PBAVE calculation part 35 GAIRTH calculation part 34 GAIRINVO calculation part

Claims (1)

An apparatus for calculating a cylinder intake air amount of an internal combustion engine,
An intake air amount sensor for detecting an intake air amount provided in an intake pipe of the internal combustion engine;
An intake pressure sensor for detecting the intake pressure of the intake pipe;
First air amount averaging means for sampling an output of the intake air amount sensor and calculating an average intake amount for each TDC section;
First intake pressure averaging means for sampling the output of the intake pressure sensor and calculating an average intake pressure for each TDC section;
A second air amount averaging means that calculates a moving average of the average intake air amount calculated by the first air amount averaging means over a plurality of TDC sections to obtain a second average intake air amount;
A second intake pressure averaging means that calculates a moving average over a plurality of TDC sections of the average intake pressure calculated by the first intake pressure averaging means to obtain a second average intake pressure;
A correction amount calculating means for obtaining a coefficient KINVO corresponding to a difference ΔPBAVE between the current value and the previous value of the second average intake pressure, and calculating a correction amount for correcting the second average intake air amount using the coefficient. When,
And a cylinder intake air amount calculation device configured to calculate the cylinder intake air amount from the second average intake amount and the correction amount.

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