JP5284854B2 - Intake air amount estimation device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake air amount estimation device for an internal combustion engine, and corrects an intake air amount detected by a sensor in accordance with a change in the opening characteristic of at least one of an intake valve and an exhaust valve. The present invention relates to an intake air amount estimation device that accurately estimates a transient intake air amount.

  In Patent Document 1, an intake system of an internal combustion engine is divided into elements such as a throttle valve, an intake pipe, and an intake valve, and each element is modeled and expressed by a mathematical expression. In other words, the invention relates to an intake air amount estimation device for an internal combustion engine using a so-called air model, in which the intake air amount (cylinder charged air amount) of the engine is obtained by calculation. Specifically, the basic cylinder charge air amount, which is the cylinder charge air amount when the engine temperature is a specific temperature, is estimated, and the basic cylinder charge air amount is determined as the engine temperature (or engine cooling water temperature). Then, correction is made based on the engine speed, the opening / closing timing of the intake valve, the pressure in the intake pipe when the exhaust valve is closed, and the (acting angle or lift amount) of the intake valve to obtain the in-cylinder charged air amount I am doing so. In such a method, since an in-cylinder charged air amount is obtained using an air model, there is a problem that a modeling error is likely to occur. In addition, when the opening / closing timing of the intake valve / exhaust valve changes, the amount of air charged in the cylinder changes immediately, and the pressure in the intake pipe changes later, but in the invention of Patent Document 1, before the change Since the cylinder air charge is estimated using the intake pipe pressure, the cylinder air charge cannot be estimated immediately in response to changes in the opening / closing timing of the intake and exhaust valves. There is a problem that arises.

  In Patent Document 2 or Patent Document 3, in an internal combustion engine equipped with a variable valve timing mechanism, a predetermined calculation is performed based on the engine speed detected by the engine rotation sensor and the intake pressure detected by the intake pressure sensor, and the cylinder inflow An invention for estimating the amount of air is shown. However, since this method does not directly detect the amount of air, there is a problem that it is not possible to compensate for secular changes in the intake system mechanism and variations among individuals.

  Patent Document 4 or Patent Document 5 discloses an invention in which the intake air amount is detected by an air flow meter, and the in-cylinder charged air amount (cylinder intake air amount) is calculated based on the detected data. In this case, it is shown that the detection response delay of the air flow meter is compensated for a transient change in the amount of air flowing through the air flow meter. However, this method only compensates for the detection response delay of the air flow meter in response to a transient change in the amount of air flowing through the air flow meter, so that the valve opening characteristics (opening / closing timing or lift amount) of the intake and exhaust valves It is not possible to compensate for the change in the intake air amount when the air pressure changes. This is because the amount of air flowing through the air flow meter itself is delayed with respect to changes in the valve opening characteristics of the intake and exhaust valves. Compensating for the detection response delay of the air flow meter is therefore the valve opening characteristics of the intake and exhaust valves. This is because it cannot be a compensation for the change of.

JP2007-40266 JP 7-301144 A JP 2005-307847 A JP 2002-130042 A JP 2007-138908 A

  If the intake air volume cannot be estimated immediately in response to changes in the valve opening characteristics of the intake and exhaust valves as seen in the above prior art, during the transition period (when the valve opening characteristics of the intake and exhaust valves change) Appropriate fuel injection control cannot be performed, and the problem of exhaust emissions worsens during the transition period.

  The present invention has been made in view of the above points, and estimates a substantial volume change (ηv volumetric efficiency change) in a cylinder with respect to a change in valve opening characteristics of at least one of an intake valve and an exhaust valve, and is detected by an air flow meter. The present invention is intended to provide an intake air amount estimation device for an internal combustion engine that can perform accurate intake air amount estimation in a transition period by correcting the intake air amount.

An intake air amount estimating apparatus for an internal combustion engine according to the present invention includes a means (13) for detecting an intake air amount (GairTH), a means (15) for detecting intake pressure (PBA), and a change in the detected intake pressure. Means (S3) for calculating a first correction value (GairINVO) related to the amount of intake pipe filling air based on the amount (ΔPBA), and the opening characteristics of at least one of the intake valve (21) and the exhaust valve (22) Based on the previous values of the change amount (dVcyl) of the actual cylinder capacity based on the change in the actual cylinder capacity (dVcyl) and the estimated value (dPBA) of the intake pressure change amount , Based on the means (S43) for calculating the cylinder charge air amount change amount (GairVTX) and the cylinder charge air amount change amount (GairVTX), a second correction value ( CairVTX) corresponding to the transient cylinder charge air amount change ( GairVT) Means ( S44) and the estimated value (dPBA) of the intake pressure change amount based on the change amount (GairVTX) of the cylinder charge air amount, and the calculated present value is used as the previous value in the next cycle. comprising a means Ru is used (S45), and means (S5) for correcting using said detected intake air amount of the first correction value (GairTH) (GairINVO) and a second correction value (GairVT) . In addition, the code | symbol described in the parenthesis above shows the corresponding | compatible component in the Example demonstrated below exemplarily.

According to the present invention, when the intake air amount is estimated, the intake air amount (AFM) actually detected is used, and the intake pipe calculated based on the change amount (ΔPBA) of the intake pressure actually detected is used. Based on correction using the first correction value (GairINVO) related to the charge air amount, and in addition, based on the change amount (GairVTX) of the cylinder charge air amount calculated according to the mathematical model, A second correction value (GairVT) corresponding to a transient cylinder charge air amount change is calculated, and the detected intake air amount (AFM) is further corrected using the second correction value (GairVT). ing. The change in the actual cylinder capacity based on the change in the valve opening characteristics of the intake valve and the exhaust valve affects the amount of intake air charged in the cylinder (cylinder). However, the means (13) for detecting the intake air amount (GairTH) and the means (15) for detecting the intake pressure (PBA) cannot perform detection in response to the change in the valve opening characteristics. By simply using the detection means, it is not possible to accurately estimate the transient change in the intake air amount when the valve opening characteristic changes. Therefore, in the present invention, the second correction value (GairVT) corresponding to the transient cylinder charge air amount change is calculated based on the change amount (GairVTX) of the cylinder charge air amount calculated according to the mathematical model. This is used for correction. That is , the change amount (dVcyl) of the actual cylinder capacity is calculated based on the change in the valve opening characteristics of at least one of the intake valve and the exhaust valve, and the change amount (GairVTX) of the cylinder charge air amount is calculated based on this change. A second correction value (GairVT) corresponding to a transient cylinder charge air amount change is calculated based on the change amount (GairVTX) of the charge air amount. The change in the valve opening characteristics of the intake valve and the exhaust valve causes a change in the pressure in the intake pipe during the next TDC cycle, which affects the amount of intake air filled in the cylinder. Therefore, when calculating the amount of change in cylinder air charge amount to (GairVTX) in accordance with the mathematical model, the previous value of the estimated value of the intake pressure change amount according to a change in the valve opening characteristics (DPBA) are incorporated in the parameters. As described above, the change amount (GairVTX) of the cylinder charge air amount calculated according to the mathematical model shows a characteristic that immediately responds to the change of the valve opening characteristic, and in this, the estimated value (dPBA) of the intake pressure change amount is shown. Since the previous value is incorporated, if this is used as it is as a correction value, there arises a problem of double correction with the first correction value (GairINVO). Therefore, in the present invention, the second correction value (GairVT) corresponding to the transient change in the cylinder charge air amount is calculated and corrected using this. Thereby, it is possible to obtain a correction parameter ( second correction value) corresponding to a transient change in the intake air amount that immediately responds to a change in the valve opening characteristics of the intake valve and the exhaust valve. By correcting the intake air amount (GairTH) actually detected by the detection means (air flow meter), it is possible to accurately estimate the intake air amount in response to a transient change .

Thus, according to the present invention, not only the detected intake air amount (AFM) is corrected using the first correction value (GairINVO) based on the detected change amount (ΔPBA) of the intake pressure, The change amount (dVcyl) of the actual cylinder capacity is calculated based on the change in the valve opening characteristic of at least one of the valve and the exhaust valve, and the calculated change amount (dVcyl) of the actual cylinder capacity and the estimated value (dPBA) of the intake pressure change amount The amount of change in the cylinder charge air amount (GairVTX) is calculated based on the previous value , and the second correction value (GairVT) corresponding to the transient cylinder charge air amount change is calculated based on the amount of change in the cylinder charge air amount. Since it is calculated and further corrected using the calculated second correction value (GairVT), a transient change correction of the intake air amount (GairTH) is made in response to changes in the valve opening characteristics of the intake and exhaust valves. Can do, intake valve and exhaust valve It will allow the estimation of the immediate response and accurate intake air amount to changes in the valve opening characteristics. In addition, since the basic intake air amount (GairTH) to be corrected can be the one actually detected by the detection means (air flow meter), there is no problem of modeling error and the aging of the mechanism of the intake system. Changes and individual variations do not cause errors. In addition, appropriate fuel injection control can be performed by appropriately estimating the intake air amount in the transition period (when the valve opening characteristics of the intake valve / exhaust valve change), and exhaust emissions in the transition period deteriorate. Can be suppressed. In addition, when combining the correction using the first correction value (GairINVO) based on the actual detection value and the correction based on the mathematical model, the correction value based on the mathematical model corresponds to a transient change in the cylinder charge air amount. The second correction value (GairVT) is used to avoid inconvenience due to double correction with the correction based on the actual detection value, so it responds immediately to changes in the valve opening characteristics of the intake and exhaust valves. Correction can be performed with high accuracy.

According to an embodiment of the present invention, the means for calculating the second correction value (GairVT) includes a current value (GairVTX (k)) and a previous value (GairVTX) of the change amount (GairVTX) of the cylinder charge air amount. The second correction value (GairVT) is calculated based on the difference from (k-1)). According to this, a transient change in the cylinder charge air amount can be calculated as a difference in the change amount of the cylinder charge air amount between adjacent TDC cycles.

1 is a block diagram showing a functional configuration of a control system to which an intake air amount estimation device for an internal combustion engine according to an embodiment of the present invention is applied.

The flowchart which shows the main flow of the intake air amount calculation process which concerns on one Example of this invention.

The flowchart which shows the detailed example of the "GairINVO calculation" routine in FIG.

The flowchart which shows the detailed example of the "GairVT calculation" routine in FIG.

5 is a flowchart showing an example of a calculation process of a substantial cylinder capacity Vcyl (k) performed in step S41 of FIG.

6 is a graph showing an example of tables # 1 and # 2 referred to in steps S51 and S52 of FIG.

5 is a flowchart showing another example of the calculation process of the substantial cylinder capacity Vcyl (k) performed in step S41 of FIG.

The graph which shows an example of table # 3 and # 4 referred by step S71 of FIG. 7, and S4.

The figure which shows the example of a waveform of each data in the process of step S44 of FIG.

The figure which shows the example of a waveform of each data at the time of changing at least one valve opening / closing timing control value CAIN and CAEX in the state which fixed the engine speed and the opening degree of the throttle valve.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Schematic functional configuration of the control system Figure 1 is a block diagram showing a functional configuration of a control system intake air quantity estimation apparatus for an internal combustion engine is applied according to an embodiment of the present invention. As is known, in the internal combustion engine 10, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting the intake air amount is provided downstream thereof. A throttle valve 14 whose opening degree is adjusted by an actuator such as a DC motor is provided on the downstream side of the air flow meter 13. An intake pressure sensor 15 for detecting the intake pipe absolute pressure PBA and an intake air temperature sensor 16 for detecting the intake air temperature Ta are provided on the downstream side of the throttle valve 14.

  An intake valve 21 and an exhaust valve 22 are provided for each cylinder (cylinder) 20 of the internal combustion engine 10, and a fuel injection valve 17 is provided for each cylinder slightly upstream of the intake valve 21. The opening timing of each injection valve 17 is controlled by an electronic fuel injection control unit (ECU) 30. The air-fuel mixture is introduced into the combustion chamber of the cylinder 20 by opening the intake valve 21, and the exhaust gas after combustion is discharged to the exhaust pipe 23 by opening the exhaust valve 22. Each of the intake valve 21 and the exhaust valve 22 is provided with a variable valve mechanism (not shown). The variable valve mechanism has a structure in which the valve opening characteristics (opening / closing timing or lift amount) of the intake valve 21 and the exhaust valve 22 can be varied continuously or stepwise. The valve opening characteristics are adjusted according to the above. As is well known, a variable valve mechanism may be provided only on one of the intake valve 21 and the exhaust valve 22.

  A signal corresponding to the rotation angle of the crankshaft generated from the crank angle position detection means 31 that detects the rotation angle of the crankshaft (not shown) of the internal combustion engine 10 is supplied to the ECU 30. The crank angle position detection means 31 is a crank angle position before a predetermined crank angle with respect to the top dead center (TDC) at the start of the intake stroke of each cylinder 20 of the internal combustion engine 10 (for example, every 180 degrees in a 4-cylinder engine). A TDC sensor that outputs a TDC pulse is included. The signal pulse generated from the crank angle position detection means 31 is used for various timing controls such as fuel injection timing and ignition timing, and detection of the engine speed NE.

  The ECU 30 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, a central processing circuit (CPU), It comprises a storage circuit for storing various calculation programs and calculation results executed by the CPU, an output circuit for supplying a drive signal to the fuel injection valve 17, and the like.

  When the ECU 30 controls the fuel injection valve 17 based on the detection signals of various sensors, the ECU 30 sets the intake air amount based on the detection signal of the air flow meter 13 to open the intake valve 21 and the exhaust valve 22 as described below. Correct according to the valve characteristics, and accurately estimate the intake air amount in consideration of the valve opening characteristics.

Explanation of the principle of intake air amount estimation according to the present invention The factor that changes the amount of intake air charged in the cylinder 20 is the presence of a valve in the intake / exhaust system. One factor is the throttle valve 14, and the amount of intake air charged into the cylinder 20 through the intake pipe 11 changes as the throttle valve opening changes. A change in the amount of intake air passing through the throttle valve due to such a change in the throttle valve opening can be calculated based on a detection signal from the air flow meter 13 with almost no response delay. Another factor is the intake valve 21 and the exhaust valve 22. When the valve opening characteristics of the intake valve 21 and the exhaust valve 22 change, the real capacity of the cylinder (cylinder) 20 changes, and accordingly, the pressure in the intake pipe 11 changes, and finally the air passing through the air flow meter 13. The amount is changed. However, with respect to the timing when the amount of air charged in the cylinder (cylinder) 20 changes in accordance with the change in the valve opening characteristics of the intake valve 21 and the exhaust valve 22, the pressure PBA in the intake pipe 11 changes accordingly. In addition, there is a delay of 1 TDC cycle at the timing when the air amount passing through the air flow meter 13 changes. Therefore, when the valve opening characteristics of the intake valve 21 and the exhaust valve 22 change, the intake air amount detected by the air flow meter 13 corresponds to the change in the valve opening characteristics of the intake valve 21 and the exhaust valve 22. This does not reflect the change in the amount of intake air filled in In order for the intake air amount detected by the air flow meter 13 to reflect the change in the intake air amount filled in the cylinder 20 in accordance with the change in the valve opening characteristics of the intake valve 21 and the exhaust valve 22, there is a delay of 1 TDC cycle. is there. Moreover, the delay of 1 TDC cycle is also caused by the fact that the pressure PBA in the intake pipe 11 reflects the change in the amount of intake air charged into the cylinder 20 in accordance with the change in the valve opening characteristics of the intake valve 21 and the exhaust valve 22. is there.

  Therefore, in the method of estimating the intake air amount based only on the detection value of the air flow meter 13 (or further considering the detection value PBA of the intake pressure sensor 15), the valve opening characteristics of the intake valve 21 and the exhaust valve 22 are estimated. There is a drawback that it is impossible to perform intake air estimation that responds quickly to changes in the air pressure. In view of this point, in the present invention, the intake air amount based on the detection value of the air flow meter 13 is corrected in accordance with the change in the valve opening characteristics of the intake valve 21 and the exhaust valve 22, so that the intake valve 21 and the exhaust valve 21 are exhausted. The intake air amount is accurately estimated in response to a change in the valve opening characteristic of the valve 22.

  Changes in the amount of intake air charged into the cylinder 20 in accordance with changes in the valve opening characteristics of the intake valve 21 and the exhaust valve 22 model changes in the state of the cylinder 20 as described below, and the intake pipe (intake). It can be estimated by modeling the state change in the manifold 11.

The state change in the cylinder 20 can be modeled by the following in-cylinder state equation.
[In-cylinder equation of state]
Pcyl ・ Vcyl = G ・ R ・ Tcyl (Formula 1)
Here, Pcyl is the pressure in the cylinder 20, Vcyl is the substantial capacity in the cylinder 20, G is the gas mass in the cylinder 20, R is a constant, and Tcyl is the gas temperature in the cylinder 20.

Since no new air flows into the intake system when the intake valve 21 is closed, it can be assumed that the cylinder pressure Pcyl is equal to the intake pressure PBA. Therefore, the above equation 1 can be rewritten as follows.
G = (PBA · Vcyl) / (R · Tcyl) (Formula 2)

Differentiating both sides of the above equation 2 gives the following (however, temperature change is not considered).
dG = (dPBA · Vcyl + PBA · dVcyl) / (R · Tcyl) (Formula 3)

  As can be seen from the in-cylinder state equation, the gas mass G in the cylinder 20, that is, the amount of charged air, is a function of the actual capacity Vcyl in the cylinder 20 and also a function of the pressure PBA in the intake pipe 11 (intake manifold). Further, the above equation 3 represents the gas mass G in the cylinder 20, that is, the change amount dG of the charged air amount, and is a function of the change amount Vcyl dVcyl and the change amount PPBA of PBA. The substantial capacity Vcyl in the cylinder 20 changes according to changes in the valve opening characteristics of the intake valve 21 and the exhaust valve 22. Therefore, by calculating Vcyl and dVcyl that change according to changes in the valve opening characteristics of the intake valve 21 and the exhaust valve 22 and putting them in the above equation 3, the change amount dG of the charged air amount according to the change in the valve opening characteristics Can be calculated. On the other hand, since PBA changes dependently in the next TDC cycle as a result of the change in Vcyl, the change dPBA used in the above equation 3 is based on the following intake manifold internal state equation in this TDC cycle. An estimated value is calculated, and the calculated estimated value of dPBA is used in the next TDC cycle.

The state change in the intake pipe 11 (intake manifold) can be modeled by the following state equation in the intake manifold.
[Intake manifold state equation]
PBA · Vinma = G · R · Ta (Formula 4)
Here, PBA is the pressure in the intake pipe, Vinma is the volume of the intake pipe 11 (intake manifold), G is the gas mass in the intake pipe 11, R is a constant, and Ta is the gas temperature in the intake pipe 11.

Differentiating both sides of the above equation 4 gives the following (however, temperature change is not considered).
dPBA ・ Vinma = dG ・ R ・ Ta
dPBA = (dG · R · Ta) / Vinma (Formula 5)

  As described above, a transient change in the amount of charged air when the valve opening characteristics of the intake valve 21 and the exhaust valve 22 are changed is calculated by a mathematical model using the in-cylinder state equation and the intake manifold state equation.

  By the way, in general, when control is performed based on such a mathematical model, it is not easy to solve problems such as model errors and mechanical individual differences of individual intake systems. Therefore, in the present invention, the estimation of the intake air amount based on the mathematical model is performed only for the estimation of the transient change in the charge air amount when the valve opening characteristics of the intake valve 21 and the exhaust valve 22 change, and the basic model is used. The intake air amount is calculated on the basis of the value actually detected by the air flow meter 13, and the basic intake air amount based on the actual detection value is estimated by the mathematical model dG. I am trying to correct by.

Description Figure 2 embodiment is a flowchart showing a main flow of the intake air amount calculation processing according to an embodiment of the present invention, is performed by a microcomputer included in the ECU 30.

  In the main flow, in the “GairAVE0 calculation” routine S1, the detection values of the air flow meter 13 are sampled at a plurality of sampling timings within one TDC cycle, and are averaged to obtain an average value of the detection values of the air flow meter 13 in one TDC cycle. Find GairAVE0. The unit of the average value GairAVE0 of the air flow meter detection value is, for example, g / sec (grams per second).

  In the next “GairTH calculation” routine S2, an air flow meter detection value GairTH is calculated by converting the unit of GairAVE0 into the number of grams per 1 TDC period.

  Note that the “GairAVE0 calculation” routine S1 and the “GairTH calculation” routine S2 are well known and will not be described in detail. Further, the present invention is not limited to the “GairAVE0 calculation” routine S1 and the “GairTH calculation” routine S2, but may be any configuration as long as the detection value of the air flow meter 13 is acquired.

  In the “GairINVO calculation” routine S3, a correction value (first correction value) GairINVO corresponding to the amount of air charged in the intake pipe 11 is calculated based on the intake pipe pressure PBA detected by the intake pressure sensor 15. The correction value GairINVO is for subtracting and correcting the air flow meter detection value GairTH in response to a change in the amount of air charged in the intake pipe 11. For example, an increase in the amount of air charged into the intake pipe 11 means a decrease in the amount of air charged in the cylinder 20, and therefore, in the subsequent step S5, the first correction value GairINVO is set to the air flow meter. It correct | amends so that it may subtract from detection value GairTH.

A detailed example of the “GairINVO calculation” routine S3 will be described with reference to FIG.
In step S31, the difference between the intake pipe pressure PBA (k) detected by the intake pressure sensor 15 in the current TDC cycle and the intake pipe pressure PBA (k-1) detected by the intake pressure sensor 15 in the previous TDC cycle. Ask for. This difference is referred to as a detected intake pressure change ΔPBA. Throughout this specification, k in parentheses at the end of the reference sign is an ordinal number indicating a TDC cycle. As a method of obtaining the intake pipe pressure PBA in the 1TDC cycle, the value of the intake pipe pressure PBA detected by the intake pressure sensor 15 at a predetermined sampling timing in the 1TDC cycle may be used, or in the 1TDC cycle. An average value of the intake pipe pressure PBA detected by the intake pressure sensor 15 at a plurality of sampling timings may be used.

In step S32, using the detected intake pressure change ΔPBA calculated in the previous step,
GairINVO = (ΔPBA · Vinma) / (R · Ta) (Formula 6)
A calculation value GairINVO for the intake air amount based on the detected intake pressure change ΔPBA per TDC cycle is calculated. The above equation 6 corresponds to the above equation 5 in the intake manifold state equation, and GairINVO represents a change in the amount of charged air in the intake pipe 11.

  Returning to FIG. 2, in the “GairVT calculation” routine S <b> 4, the intake air amount correction value (second value) corresponding to a transient change in the charged air amount when the valve opening characteristics of the intake valve 21 and the exhaust valve 22 change. Correction value) GairVT is calculated.

A detailed example of the “GairVT calculation” routine S4 will be described with reference to FIG.
In steps S41 and S42, a change amount dVcyl of the substantial cylinder capacity Vcyl is calculated based on changes in the valve opening characteristics of the intake valve 21 and the exhaust valve 22. Specifically, in step S41, the actual cylinder capacity Vcyl (k) in the current TDC cycle is calculated based on the intake valve opening / closing timing control value CAIN and the exhaust valve opening / closing timing control value CAEX in the current 1TDC cycle. These valve opening / closing timing control values CAIN and CAEX are generated in the ECU 30 in accordance with the accelerator opening, the engine operating state, etc., as is well known, and control the variable valve mechanisms of the intake valve 21 and the exhaust valve 22 described above. It is used to do. In step S41, the actual cylinder capacity Vcyl (k) is calculated using these valve opening / closing timing control values CAIN and CAEX.

  As is well known, the intake valve opening / closing timing control value CAIN and the exhaust valve opening / closing timing control value CAEX indicate the advance angle or delay angle with respect to each predetermined valve opening reference timing based on the crank angle. For example, when CAEX changes in the forward direction, the exhaust valve 22 closes earlier than the top dead center, so that residual gas remains in the cylinder, and the substantial cylinder capacity decreases (the volume that can be filled decreases). When the CAIN changes in the delay direction, the intake valve 21 closes later than the bottom dead center, thereby reducing the substantial cylinder capacity.

  FIG. 5 shows a detailed example of the calculation process of the substantial cylinder capacity Vcyl (k) performed in step S41 of FIG. In the ECU 30, a table # 1 storing a cylinder charge air amount Vcylin corresponding to the intake valve opening / closing timing control value CAIN, and a table # 2 storing a cylinder exhaust air amount Vcylex corresponding to the exhaust valve opening / closing timing control value CAEX, It has. FIGS. 6A and 6B show an example of the contents of these tables # 1 and # 2.

  In FIG. 5, in step S51, the cylinder filling air amount Vcylin (k) in the current TDC cycle is retrieved (acquired) from the table # 1 based on the intake valve opening / closing timing control value CAIN. In step S52, the cylinder exhaust air amount Vcylex (k) in the current TDC cycle is retrieved (acquired) from the table # 2 based on the intake valve opening / closing timing control value CAEX. In step S53, the difference between the cylinder charge air amount Vcylin (k) and the cylinder exhaust air amount Vcylex (k) is calculated as a substantial cylinder capacity Vcyl (k). That is, the difference between the air amount Vcylin (k) charged in the cylinder 20 and the air amount Vcylex (k) discharged from the cylinder 20 is the substantial cylinder capacity Vcyl (k).

  When the variable valve mechanisms of the intake valve 21 and the exhaust valve 22 are variable valve lift mechanisms, tables # 1 and # 2 as shown in FIGS. 6A and 6B are provided for each lift amount. To prepare for. That is, the tables # 1 and # 2 are selected according to the current valve lift amount, and the cylinder charge air amount Vcylin (k) and the cylinder according to the valve opening / closing timing control values CAIN and CAEX are selected from the selected tables # 1 and # 2. The exhaust air amount Vcylex (k) is searched. Tables # 1 and # 2 for each lift amount have a substantial cylinder capacity as the exhaust valve closes earlier with respect to the top dead center and the intake valve closes later with respect to the bottom dead center due to the change in the valve lift amount. It tends to decrease.

  FIG. 7 shows another example of the calculation process of the substantial cylinder capacity Vcyl (k) performed in step S41 of FIG. In this example, the actual cylinder capacity Vcyl (k) is calculated in consideration of the engine speed NE in addition to the valve opening / closing timing control values CAIN and CAEX. This is intended to take into account the ease of air entering and leaving the cylinder 20 depending on the engine speed NE even at the same valve opening / closing timing. In this example, the ECU 30 includes the tables # 1 and # 2, and further stores the inflow correction coefficient KVcylin corresponding to the engine speed NE and the exhaust correction corresponding to the engine speed NE. And a table # 4 storing the coefficient KVcylex. FIGS. 8A and 8B show an example of the contents of these tables # 3 and # 4.

  In FIG. 7, in step S71, the cylinder charge air amount Vcylin ′ (k) in the current TDC cycle is retrieved (acquired) with reference to the table # 1 as in step S51 of FIG. In step S72, the inflow correction coefficient KVcylin (k) in the current TDC cycle is retrieved (obtained) from the table # 3 based on the engine speed NE. In step S73, the cylinder filling air amount Vcylin (k) in the current TDC cycle is calculated by multiplying the inflow correction coefficient KVcylin (k) by the cylinder filling air amount Vcylin '(k).

  In step S74, as in step S52 of FIG. 5, the cylinder exhaust air amount Vcylex ′ (k) in the current TDC cycle is searched (acquired) with reference to the table # 2. In step S75, the exhaust correction coefficient KVcylex (k) in the current TDC cycle is searched (obtained) from the table # 4 based on the engine speed NE. In step S76, the exhaust correction coefficient KVcylex (k) is multiplied by the exhaust air amount Vcylex '(k) to calculate the cylinder exhaust air amount Vcylex (k) in the current TDC cycle.

  In step S77, as in step S53 of FIG. 5, the difference between the cylinder charge air amount Vcylin (k) and the cylinder exhaust air amount Vcylex (k) is calculated as the substantial cylinder capacity Vcyl (k).

  Returning to FIG. 4, in step S42, the difference between the actual cylinder capacity Vcyl (k) in the current TDC cycle calculated in step S41 and the actual cylinder capacity Vcyl (k-1) in the previous TDC cycle is obtained, and the actual cylinder capacity is obtained. The change amount dVcyl (k) is calculated.

In step S43, the opening characteristics of the intake valve 21 and the exhaust valve 22 according to the above equation 3 using the actual cylinder capacity Vcyl (k) and its change dVcyl (k) in the current TDC cycle calculated as described above. The data GairVTX (k) corresponding to the change dG of the transient charge air amount at the time of change is calculated. In particular,
GairVTX (k) = {dPBA (k-1) .Vcyl (k) + PBA (k) .dVcyl (k)} / {R.Ta (k)}
Perform the operation. In Equation 3, the gas temperature Tcyl in the cylinder 20 is used as a variable. However, in the calculation in step S43, the data of the intake air temperature Ta detected by the intake air temperature sensor 16 is used as an alternative for convenience. Yes. Here, dPBA (k−1) is an estimated value of the change dPBA in the intake pipe pressure PBA in the previous TDC cycle, and the value calculated in step S45 in the previous TDC cycle is used. As PBA (k), the intake pipe pressure PBA detected by the intake pressure sensor 15 in the current TDC cycle may be used.

  In step S44, data GairVTX (k) corresponding to the change in the transient charge air amount calculated in the current TDC cycle and data GairVTX corresponding to the change in the transient charge air amount calculated in the previous TDC cycle. The difference from (k-1) is obtained, and this difference is calculated as a correction value (second correction value) GairVT for the intake air amount. In addition, in the data GairVTX (k) calculated based on the mathematical model of Equation 3, in addition to the change dVcyl of the substantial cylinder capacity corresponding to the change of the valve opening characteristic, the estimated value of the change dPBA of the intake pipe pressure PBA is also calculated. Has been taken into account. However, in the present invention, the intake air amount is corrected using the first correction value GairINVO based on the detected intake pressure change ΔPBA. Therefore, if the data GairVTX (k) calculated based on the mathematical model of Equation 3 is used as it is, double correction with correction by the first correction value GairINVO based on the detected intake pressure change ΔPBA will result. Therefore, by subtracting the data GairVTX (k−1) calculated in the previous TDC cycle from the data GairVTX (k) calculated in the current TDC cycle in step S44, the second correction value GairVT is used. Double correction is not used.

  FIG. 9 shows a waveform example of each data in the process of step S44. In FIG. 9A, the solid line shows an example of a data waveform in which data GairVTX (k) corresponding to the transient change in the amount of charged air calculated in the current TDC cycle is plotted along the time axis. A section that changes in a mountain shape is a section in which a transient change in the amount of charged air occurs, and this change section includes a plurality of TDC cycles. The broken line is a plot of the data GairVTX (k-1) calculated in the previous TDC cycle along the time axis. In short, the dotted line waveform is obtained by delaying the solid line waveform by the time of 1 TDC cycle. FIG. 9B shows a waveform of the second correction value GairVT (k) obtained by subtracting GairVTX (k-1) from GairVTX (k).

  Since the second correction value GairVT indicates the amount of air charged in the cylinder 20, in the subsequent step S5, the second correction value GairVT is corrected so as to be added to the air flow meter detection value GairTH. To do.

In step S45, the data GairVTX (k) corresponding to the actual cylinder capacity Vcyl (k), its change amount dVcyl (k) and the change amount dG of the transient charge air amount in the current TDC cycle calculated as described above are obtained. The estimated value dPBA (k) of the change amount dPBA of the intake pipe pressure PBA is calculated according to the equation (5). In particular,
dPBA (k) = {GairVTX (k) · R · Ta (k)} / Vinma
Perform the operation. The calculated estimated value dPBA (k) is used as the estimated value dPBA (k-1) of the change dPBA in the intake pipe pressure PBA in the previous TDC cycle in the calculation in step S43 in the next TDC cycle.

  Returning to FIG. 2, in step S5, the first correction value GairINVO is subtracted from the air flow meter detection value GairTH, and the second correction value GairVT is added to correct the air flow meter detection value GairTH. As a result, the intake air amount estimated value GairCYL that immediately responds to the change in the transient charge air amount when the valve opening characteristics of the intake valve 21 and the exhaust valve 22 change is calculated.

  FIG. 10 shows a waveform example of each data in the above embodiment when at least one of the valve opening / closing timing control values CAIN and CAEX is changed with the engine speed NE and the opening degree of the throttle valve 14 fixed. . (A) shows the example of a change of at least one valve opening / closing timing control value CAIN, CAEX. (B) shows the estimated intake air amount GairCYL calculated in accordance with the present invention in response to this change, and the airflow meter detected value GairTH. (C) shows the time change of the intake pipe pressure PBA. (D) shows a time change of the first correction value GairINVO calculated based on the detected intake pipe pressure PBA. Since GairINVO is subtracted from GairTH, when the first correction value GairINVO is a negative value, it becomes an increase value with respect to GairTH. (E) shows the time change of the second correction value GairVT. Since GairVT is added to GairTH, when the second correction value GairVT is a positive value, it becomes an increase value with respect to GairTH, and when it is a negative value, it becomes a decrease value with respect to GairTH. The vertical scale of (e) is drawn at about 10 times the vertical scale of (d). That is, the second correction value GairVT is smaller than the first correction value GairINVO. As can be seen from (b), the change in the air flow meter detection value GairTH is considerably delayed with respect to the change in the valve opening / closing timing control values CAIN and CAEX. On the other hand, it can be seen that the intake air amount estimated value GairCYL calculated according to the present invention responds quickly to changes in the valve opening / closing timing control values CAIN and CAEX.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Intake pipe 12 Air cleaner 13 Air flow meter 14 Throttle valve 15 Intake pressure sensor 16 Intake temperature sensor 17 Fuel injection valve 20 Cylinder (cylinder)
21 Intake valve 22 Exhaust valve 30 Electronic fuel injection control device (ECU)

Claims (2)

Means for detecting the amount of intake air;
Means for detecting the intake pressure;
Means for calculating a first correction value related to the intake pipe filling air amount based on the detected change amount of the intake pressure;
Means for calculating a change amount of the substantial cylinder capacity based on a change in valve opening characteristics of at least one of the intake valve and the exhaust valve;
Means for calculating the change amount of the cylinder charge air amount based on the previous value of the change amount of the substantial cylinder capacity and the estimated value of the intake pressure change amount;
Means for calculating a second correction value corresponding to a transient cylinder charge air amount change based on the change amount of the cylinder charge air amount ;
Calculating the present value of the estimated value of the intake pressure change amount on the basis of the change amount of the cylinder air charge amount, and means Ru is used the current value of the calculated as the previous value in the next cycle,
An intake air amount estimation device for an internal combustion engine, comprising: means for correcting the detected intake air amount using the first correction value and the second correction value. The means for calculating the second correction value calculates the second correction value based on a difference between a current value and a previous value of a change amount of the cylinder charge air amount. Intake air amount estimation device for internal combustion engine of

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