JP3268143B2 - Exhaust gas recirculation rate estimation device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation rate estimating apparatus for an internal combustion engine, and more particularly, to an apparatus for estimating the recirculation rate of exhaust gas flowing into an engine combustion chamber in a simple and accurate manner. The present invention relates to an exhaust gas recirculation rate estimation device. Here, “exhaust gas recirculation rate” means a volume ratio or a weight ratio of exhaust gas / intake air.

[0002]

2. Description of the Related Art An exhaust gas recirculation passage connecting an exhaust passage and an intake passage of an internal combustion engine is provided to recirculate a part of exhaust gas to the intake passage, and an exhaust gas recirculation valve is provided therein to control a recirculation amount. In the exhaust gas recirculation control for reducing NOx and improving the fuel efficiency, in order to perform the exhaust gas recirculation control with high accuracy, the recirculation rate of the exhaust gas actually flowing into the combustion chamber (hereinafter referred to as “net recirculation rate”) or the exhaust gas recirculation rate It is necessary to estimate the flow rate accurately. Further, since the exhaust gas recirculation amount becomes a disturbance when controlling the air-fuel ratio or the fuel injection amount of the internal combustion engine, it is necessary to accurately estimate the exhaust gas recirculation rate or the exhaust gas recirculation amount in that sense.

Japanese Patent Application Laid-Open No. 4-311643 estimates the partial pressure and total pressure of the recirculated gas and air in the intake passage from the amount of the recirculated gas flowing into the intake passage, and then estimates the amount of air flowing into the cylinder. Is calculated. However, in this method, in order to obtain the partial pressure of the recirculated gas, it is necessary to accurately obtain not only the amount of the recirculated gas flowing into the intake passage but also the intake air temperature and the chamber volume, which requires complicated calculations. It is extremely difficult to accurately determine the amount of inflow of the recirculated gas into the intake passage due to the dynamic delay of the recirculated gas.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to reduce the number of complicated calculations and uncertain arithmetic elements as much as possible. It is an object of the present invention to provide an exhaust gas recirculation rate estimating apparatus for an internal combustion engine, which is capable of accurately obtaining a recirculation rate of exhaust gas flowing into a combustion chamber.

Further, when controlling the fuel injection amount so that the air-fuel ratio becomes the target value, the exhaust gas flowing into the combustion chamber is
Disturbance.

Accordingly, a second object of the present invention is to reduce the number of complicated calculations and uncertain arithmetic elements as much as possible, and to obtain the recirculation rate of exhaust gas flowing into the combustion chamber with high accuracy while having a simple configuration. An object of the present invention is to provide an apparatus for estimating an exhaust gas recirculation rate of an internal combustion engine, which corrects a fuel injection amount accurately.

Furthermore, the exhaust gas flowing into the combustion chamber reduces the ignitability of the air-fuel mixture, and thus becomes a disturbance in the ignition timing control.

Accordingly, a third object of the present invention is to reduce the number of complicated calculations and uncertain calculation elements as much as possible, and to obtain the recirculation rate of exhaust gas flowing into the combustion chamber with high accuracy while having a simple configuration. An object of the present invention is to provide an apparatus for estimating an exhaust gas recirculation rate of an internal combustion engine, which corrects an ignition timing accurately.

[0009]

According to a first aspect of the present invention, an exhaust passage and an intake passage of an internal combustion engine are connected to each other so that at least a part of exhaust gas is supplied to the intake passage. An internal combustion engine comprising: an exhaust gas recirculation passage that recirculates to a passage; and an exhaust recirculation valve that opens and closes the exhaust gas recirculation passage, wherein the internal combustion engine includes at least an engine speed and an engine load for each predetermined detection cycle. Operating state detecting means for detecting an operating state; exhaust gas recirculation valve operation state detecting means for detecting an operation state of the exhaust gas recirculation valve at each of the predetermined detection periods; and the exhaust gas flows into the combustion chamber through the exhaust gas recirculation valve obtains the dead time until the reflux from the detected operating state and the operating state of the exhaust gas recirculation valve before detection period corresponding to the dead time, the exhaust gas flowing into the combustion chamber through the exhaust gas recirculation valve Rate Exhaust gas recirculation rate calculating means for output, and
The calculated exhaust reflux rate with <br/> the exhaust gas recirculation rate determining means regarded as recirculation ratio of exhaust gas flowing into the combustion chamber of the internal combustion engine Rutotomoni, said exhaust gas recirculation rate calculating means, at least
Determine the basic exhaust gas recirculation rate from the engine speed and engine load
Basic exhaust gas recirculation rate determining means,
Based on the detected value of the opening area of the exhaust gas recirculation valve,
First estimation for estimating the amount of exhaust gas passing through the exhaust gas recirculation valve
Means, based on the flow characteristics of the exhaust gas recirculation valve,
The gas passes through the exhaust gas recirculation valve according to the opening area command value of the flow valve.
Second estimating means for estimating the exhaust gas amount,
First, the ratio of the exhaust gas amount estimated by the second estimating means is calculated.
Therefore, the basic exhaust gas recirculation rate is corrected according to the obtained ratio.
The recirculation rate of exhaust gas flowing into the combustion chamber of the internal combustion engine.
It comprised so that it might consist of the calculation means which calculates .

[0010]

[0011] In claim 2, wherein, more specifically, the dead time is configured as determined in accordance with the operation state of the internal combustion engine.

[0012] To achieve the second object, in claim 3, wherein said exhaust gas recirculation rate determining means corrects the fuel injection amount to be supplied to the combustion chamber of the internal combustion engine in accordance with the exhaust gas recirculation rate And a correction coefficient calculating means for obtaining a correction coefficient to be performed.

[0013] To achieve the third object, according to claim 4, wherein said exhaust gas recirculation rate determining means, the correction coefficient calculation for obtaining the correction coefficient for correcting the ignition timing of the internal combustion engine in accordance with the exhaust gas recirculation rate It was configured to have means.

In order to achieve the first to third objects,
According to claim 5, wherein, more specifically, the exhaust gas recirculation rate determining means sequentially stores at least one of the exhaust gas recirculation rate and the correction coefficient is previously calculated for each calculation cycle synchronized with the predetermined detection period comprising a storage unit, and as configured to select at least one of the exhaust gas recirculation rate and the correction coefficient stored in the storage means in response to the dead time.

[0015]

[Action] According to claim 1, wherein obtains a dead time until the exhaust gas flows into the combustion chamber through the exhaust gas recirculation valve, Mu said from the detected operating state and the operating state of the exhaust gas recirculation valve before detection period corresponding to <br/> uselessly time, the exhaust gas recirculation rate calculating means for calculating a recirculation rate of the exhaust gas flowing into the combustion passes through the exhaust gas recirculation valve chamber, and the calculated exhaust gas recirculation rate The exhaust gas recirculation rate determining means, which is regarded as the recirculation rate of the exhaust gas flowing into the combustion chamber of the internal combustion engine, is configured so that complicated calculations and uncertain calculation elements can be reduced as much as possible, and a simple configuration can be used. In addition, the recirculation rate of the exhaust gas flowing into the combustion chamber can be accurately determined. Here, the dead time may be variable according to the operating state, or may be a fixed value according to the structure of the engine.

Furthermore, said exhaust gas recirculation ratio calculating means determines the basic exhaust gas recirculation ratio from the engine speed and the engine load, based on the flow characteristics of the exhaust gas recirculation valve opening area detected value of the exhaust gas recirculation valve and command The amount of exhaust gas passing through the exhaust gas recirculation valve is estimated according to the value, and the basic exhaust gas recirculation rate is corrected from the ratio to calculate the recirculation rate of the exhaust gas flowing into the combustion chamber of the internal combustion engine. In other words, since the behavior of the exhaust gas recirculation gas is grasped from the flow characteristics of the exhaust gas recirculation valve, complicated calculations and uncertain computational elements can be reduced as much as possible. It is possible to accurately estimate the net exhaust gas recirculation rate sucked into the chamber.

[0017] According to claim 2, wherein, since the dead time is configured as determined in accordance with the operating condition of the internal combustion engine, the recirculation ratio of the exhaust gas flowing into the combustion chamber can be determined more accurately .

According to the third aspect of the present invention, since the correction coefficient for correcting the fuel injection amount is determined according to the exhaust gas recirculation rate, complicated calculations and uncertain calculation elements can be reduced as much as possible. In spite of the simple configuration, the net exhaust gas recirculation rate actually sucked into the combustion chamber can be accurately estimated, and the fuel injection amount can be appropriately corrected based on that.

According to a fourth aspect of the present invention, since the correction coefficient for correcting the ignition timing is determined according to the exhaust gas recirculation rate, complicated calculations and uncertain calculation elements can be reduced as much as possible. Although the configuration is simple, the net exhaust gas recirculation rate actually sucked into the combustion chamber can be accurately estimated, and the ignition timing can be appropriately corrected based on that.

[0020] In the 5 claims, advance exhaust gas recirculation rate calculated and sequentially stores at least one correction factor, wherein stored in the storage means in accordance with the dead time the exhaust for each calculation cycle Since at least one of the recirculation rate and the correction coefficient is selected, the recirculation rate of the exhaust gas flowing into the combustion chamber or the fuel injection correction coefficient can be more easily obtained. Note that an operating state detection value or the like necessary for calculating the exhaust gas recirculation rate or the correction coefficient is stored, selected according to the dead time, and the exhaust gas recirculation rate or the fuel injection correction coefficient is obtained for the first time based on the selected value. You may do it.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram showing an exhaust gas recirculation rate estimating apparatus for an internal combustion engine according to the present invention. The internal combustion engine is, for example, a four-cylinder internal combustion engine, and a throttle valve 3 is provided in the middle of an intake pipe (intake passage) 2 of the engine body 1. A throttle position sensor (indicated by θTH) 4 for detecting a throttle position θTH is connected to the throttle valve 3, and supplies an output to an electronic control unit (hereinafter referred to as “ECU”) 5.

The ECU 5 shapes input signal waveforms from the throttle position sensor 4 and a sensor group to be described later, corrects a voltage level to a predetermined level, and converts an analog signal to a digital signal value. CPU
5b, a storage means 5c for storing various operation programs executed by the CPU 5b, operation results, and the like, and an output circuit 5d.

The fuel injection valve 6 is provided for each cylinder between the engine body 1 and the throttle valve 3 and upstream of an intake port (not shown) of a combustion chamber (not shown). The fuel injection valve 6 is connected to a fuel pump (not shown).
It is electrically connected to U5. On the other hand, an absolute pressure sensor (indicated by PBA) 7 for detecting the intake pipe pressure PBA as an absolute pressure is provided downstream of the throttle valve 3, and an intake air temperature sensor (indicated by TA) for detecting the intake air temperature TA is provided downstream thereof. ) 8 is provided. The outputs of these sensors are also sent to the ECU 5.

The engine body 1 is provided with a water temperature sensor (indicated by TW) 9 for detecting an engine cooling water temperature TW, and a crankshaft or camshaft (both not shown) is provided with a TW.
A crank angle sensor (indicated by CRK) 10 for detecting a predetermined crank angle CRK including a DC position, and a cylinder discrimination sensor (CY for detecting a predetermined crank angle CYL of a specific cylinder)
11 are provided. The output of these sensors is also E
The output of the crank angle sensor CRK is sent to the CU 5 via a counter (not shown), and the engine speed NE is counted.
Is detected.

The exhaust pipe (exhaust passage) 13 of the engine body 1
Is provided with a catalytic converter 14 for purifying HC, CO, NOx components and the like in the exhaust gas. A wide-range air-fuel ratio sensor (denoted by LAF) 15 for detecting the oxygen concentration in the exhaust gas in a wide range from rich to lean around the stoichiometric air-fuel ratio is mounted upstream of the catalytic converter 14, and supplies an output to the ECU 5.

Further, an atmospheric pressure sensor (denoted by PA) 16 for detecting an atmospheric pressure PA is provided near the engine body 1, and a wall temperature TC is detected on a wall surface of the intake pipe 2 near the intake port. A wall temperature sensor (indicated by TC) 17 is provided. The outputs of these sensors are also supplied to the ECU 5.

Next, the exhaust gas recirculation mechanism 25 will be described.

The exhaust gas recirculation passage 25 includes an exhaust gas recirculation passage 18 connecting the exhaust pipe 13 to the intake pipe 2 (reference numeral 18a).
Indicates an open end on the intake pipe side). An exhaust gas recirculation valve (EGR valve) 19 is provided in the exhaust gas recirculation passage 18. The exhaust gas recirculation valve 19 is of a negative pressure responsive type,
And a valve element 19a arranged to open and close the
The diaphragm 19b is connected to a and operates by a negative pressure introduced through an electromagnetic valve 22 described later, and a spring 19c for urging the diaphragm 19b in the valve closing direction.

A communication passage 20 is connected to a negative pressure chamber 19d defined by the diaphragm 19b, and a negative pressure in the intake pipe 2 is applied to a normally closed solenoid valve 22 provided in the middle of the communication passage 20.
It is configured to be introduced via Atmospheric chamber 19e
Is in communication with the atmosphere. Further, an atmosphere communication path 23 is connected to the communication path 20 downstream of the solenoid valve 22.
Atmospheric pressure is introduced into the communication passage 20 through the orifice 21 provided in the middle of the above, and then into the negative pressure chamber 19d.

The solenoid valve 22 is connected to the ECU 5,
The exhaust gas recirculation valve 19 is activated by a drive signal from the CU 5.
The lift operation (valve opening operation) of the valve body 19a and the speed thereof are controlled. The exhaust gas recirculation valve 19 is provided with a lift sensor 24, which detects the operation amount (lift amount) of the valve body 19a and sends an output to the ECU 5. Further, the ECU 5 calculates the fuel injection amount, controls the fuel injection amount to be supplied to the engine combustion chamber via the valve opening time of the fuel injection valve 6, calculates the ignition timing, and calculates the ignition timing via ignition means (not shown). To ignite the mixture in the engine combustion chamber.

Here, as described below, the ECU 5 estimates the exhaust gas recirculation rate, and corrects the fuel injection amount or the ignition timing based on the estimated value.

FIG. 2 is a flow chart for explaining the operation of estimating the exhaust gas recirculation rate.

Prior to the description of the figure, the algorithm of the estimation operation according to the present invention will be described with reference to FIG.

The amount of gas passing through the exhaust gas recirculation valve is determined by the opening area of the valve and the pressure ratio between the front and rear of the valve, that is, the flow characteristics (design specifications). That is, it is considered that the value is obtained from the ratio between the opening area of the valve, that is, the lift amount and the pressure between the upstream and downstream of the valve.

As shown in FIG. 3 also in the actual machine, the amount of recirculated gas is obtained by calculating the lift amount of the valve and the ratio between the atmospheric pressure PA acting through the atmosphere communication passage 23 and the intake pressure PBA of the intake pipe 2. Thus, it is considered that estimation can be made to a certain extent (actually, the flow rate characteristics slightly change depending on the exhaust pressure and the exhaust temperature, but the change in the characteristics can be absorbed to a considerable extent by using the gas amount ratio as described later). Conceivable).

Therefore, attention was first paid to this point, and the reflux rate was determined based on the flow characteristics. Note that the opening area is obtained from the lift amount, because a valve having a structure in which the lift amount corresponds to the opening area was used. Therefore, when using another structure such as a linear solenoid, the opening area is obtained from another parameter.

The recirculation rate includes a steady-state recirculation rate and a transient recirculation rate. Among them, the steady-state recirculation rate is a value in a state where the lift command value is equal to the actual lift. The recirculation rate is a value when the lift command value is not equal to the actual lift as shown in FIG. Then, in the algorithm according to the present invention, it was considered that the difference at the transient time was caused by the shift of the reflux rate from the steady-state reflux rate by the corresponding gas amount ratio as shown in FIG.

Specifically, in the steady state, the lift command value = the actual lift, the gas amount ratio = 1, that is, the recirculation rate = the recirculation rate in the steady state

In the transient state, the lift command value ≠ the actual lift, the gas amount ratio ≠ 1.

As described above, it was considered that the net recirculation rate flowing into the combustion chamber was obtained by multiplying the ratio of the two gas amounts by the recirculation rate in a steady state. The expression is as follows. Net reflux rate = (steady-state reflux rate) x (gas amount QACT obtained from actual lift and pressure ratio before and after valve) / (gas amount QCMD obtained from lift command value and pressure ratio before and after valve)

Here, the recirculation rate in the steady state is obtained by obtaining a recirculation rate correction coefficient and subtracting it from 1. That is,
When the steady-state reflux rate correction coefficient is referred to as KEGRMAP, the steady-state reflux rate = (1−KEGRMAP).

In this specification, the steady state recirculation rate or the steady state recirculation rate correction coefficient is also referred to as a basic exhaust gas recirculation rate or a basic exhaust gas recirculation rate correction coefficient. The steady-state recirculation rate correction coefficient KEGRMAP is determined by the engine speed NE and the intake pressure P.
A map was obtained in advance by experiment from BA and set as a map as shown in FIG. 5, and the map was searched for.

In the exhaust gas recirculation control, the lift command value of the exhaust gas recirculation valve is determined from the engine speed and the engine load, etc., but as shown in FIG. Value) has a delay. Further, there is a delay in the flow of the recirculated gas into the combustion chamber in accordance with the valve opening operation.

Therefore, the present applicant has previously disclosed in Japanese Patent Laid-Open No. 5-118.
In No. 239, the ratio of the amount of the recirculated gas that has passed through the exhaust gas recirculation valve to the amount that has flowed into the combustion chamber during the control cycle is defined as a direct ratio, and the ratio of the recirculated gas that has passed before that and stays in the space to the combustion chamber In addition, a model for describing the behavior of the recirculated gas was established, in which the ratio of the amount of gas flowing into the combustion chamber during the control cycle was taken as the carry-out rate, and a technique for estimating the net recycle rate based on the model was proposed.

However, as a result of further consideration of the behavior of the recirculated gas, it is better to consider that the recirculated gas that has passed through the exhaust gas recirculation valve flows into the combustion chamber at a time after a certain dead time has elapsed. It turned out to be easy.
Therefore, the above-described net recirculation rate is calculated for each predetermined cycle and stored in the storage means, and the calculated value of the past cycle corresponding to the dead time is used to calculate the recirculation rate of the exhaust gas truly flowing into the combustion chamber. I considered it.

Hereinafter, the operation of the apparatus according to the embodiment will be described with reference to the flowchart of FIG. The program shown in this flowchart is started at each TDC position.

First, at S10, the engine speed NE and the intake pressure P
BA, atmospheric pressure PA, actual lift LACT (lift sensor 2
4) is read, and the routine proceeds to S12, where a lift command value LCMD is retrieved from the engine speed NE and the intake pressure PBA. Here, the lift command value LCMD is obtained by searching a map in which characteristics are determined and set in advance as shown in FIG.

The program then proceeds to S14 in which the map shown in FIG. 5 is retrieved from the engine speed NE and the intake pressure PBA to retrieve the basic exhaust gas recirculation rate correction coefficient KEGRMAP.

Then, the program proceeds to S16, where the detected actual lift L
ACT is not zero, that is, the exhaust gas recirculation valve 1
After confirming that the valve 9 is open, the process proceeds to S18, where the retrieved lift command value LCMD is compared with a predetermined lower limit value LCMDLL (small value).

When it is determined in S18 that the search value is not lower than the lower limit value, the process proceeds to S20, in which a ratio PBA / PA between the intake pressure PBA and the atmospheric pressure PA is obtained, and from the retrieved lift command value LCMD, A map (not shown) of the characteristics shown in FIG. 3 is retrieved to determine the gas amount QCMD. This is the "gas amount obtained from the lift command value and the pressure ratio before and after the valve" in the above formula.

Then, the program proceeds to S22, in which the detected actual lift L
From the ratio PBA / PA similar to ACT, a map (not shown) of the characteristic shown in FIG. 3 is similarly retrieved to obtain the gas amount QACT. This is equivalent to the "gas amount obtained from the pressure ratio between the actual lift and the pressure before and after the valve" in the above formula.

Subsequently, the program proceeds to S24, in which a value obtained by subtracting the retrieved basic exhaust gas recirculation rate correction coefficient KEGRMAP from 1 is defined as a steady gas recirculation rate (basic exhaust gas recirculation rate or steady state recirculation rate). Here, the steady-state recirculation rate is, as described above, a recirculation rate when the exhaust gas recirculation operation is stable, that is, is not in a transient state such as when the exhaust gas recirculation operation is started or stopped. Means the reflux rate.

Then, the program proceeds to S26, where the net reflux rate is determined by multiplying the steady-state reflux rate by the ratio QACT / QCMD of the values QACT and QCMD, as shown in the figure.

Then, the program proceeds to S28, in which a fuel injection correction coefficient KEGRN is calculated. FIG. 7 is a subroutine flowchart showing the operation.

Referring to the figure, in S100, the net recirculation rate (determined in S26 of FIG. 2) is subtracted from 1, and the value is set as a fuel injection correction coefficient KEGRN.

Then, the program proceeds to S102, in which the calculated fuel injection correction coefficient KEGRN is stored (stored) in the ring buffer. FIG. 8 is an explanatory diagram showing the configuration of the ring buffer, which is provided in the storage unit 5c of the ECU 5 described above.

As shown, the ring buffer has n addresses, and each address is specified with a number from 0 to n. Then, the flow chart of FIG. 2 (and FIG. 7) is started at TDC and the fuel injection correction coefficient KEGRN
Is calculated and stored (updated) sequentially from the top in the figure.

Then, the program proceeds to S104, in which a map is retrieved from the detected engine speed NE and the engine load, for example, the intake pressure PBA, to find a dead time τ. FIG. 9 is an explanatory diagram showing the characteristics.

That is, the above-mentioned dead time indicates a delay time until the recirculated gas passing through the exhaust gas recirculation valve flows into the combustion chamber, and varies depending on the engine speed and the engine load, for example, the intake pressure. is there. Where the dead time τ
Is more specifically indicated by the buffer number.

Subsequently, the process proceeds to S106, where the calculated value (fuel injection correction coefficient KEG) stored at the corresponding address is determined based on the found dead time τ (more specifically, the buffer number).
RN). That is, as shown in FIG. 10, when the current time point is A, for example, the calculated value 12 times before is selected,
This is set as the current fuel injection correction coefficient KEGRN.

This can be seen from the operation of the exhaust gas recirculation valve.
The previous fuel injection correction coefficient KEGRN was 1.0, which means that the exhaust gas recirculation valve was closed.
Thereafter, the fuel injection correction coefficient KEGRN becomes, for example, 0.9.
9, 0.98 or the like, which gradually decreases, in other words, the exhaust gas recirculation valve is opened to reach the current time point A. However, in the illustrated example, at the current time point, the recirculated gas has not yet flowed into the combustion chamber. Therefore, the fuel injection decrease correction is not performed.

At the same time, the determined fuel injection correction coefficient KEG
The fuel injection amount is corrected based on RN. This fuel injection amount is corrected by multiplying the basic fuel injection amount Tim obtained from the engine speed and the engine load by the correction coefficient KEGRN to obtain the output fuel injection amount Tout. Stop at the description.

Returning to the flow chart of FIG.
When the actual lift LACT is determined to be zero in step 6, exhaust gas recirculation is not performed, but the fuel injection correction coefficient KEGRN is determined from the value after the dead time τ has elapsed.
Proceeding thereafter, the net recirculation rate and the fuel injection correction coefficient KEGRN
Is calculated. In this case, the net recirculation rate is set to 0 in S26, and the fuel injection correction coefficient KE is set in S100 of the flow chart of FIG.
GRN is determined to be 1.0.

If it is determined in step S18 that the lift command value LCMD is equal to or smaller than the lower limit value LCMDLL, the process proceeds to step S32.
As the lift command value LCMD, the previous value LCMDn-1 is held as it is (for simplicity, adding n to the current value in this flowchart is omitted).

This is because the dynamic characteristics of the exhaust gas recirculation valve 19 have a delay even when the lift command value LCMD becomes zero when the region shifts from the region where the exhaust gas recirculation is performed to the region where the exhaust gas recirculation is not performed.
Since the actual lift LACT does not immediately become zero, when the lift command value LCMD is equal to or lower than the lower limit (threshold) LCMDLL, the lift command value LCMD is set to the previous value LCMDn-1 (the value at the time of the previous control cycle n-1). To hold it. This previous value hold is performed by the actual lift LA in S16.
This is performed until it is confirmed that CT has become zero.

The lift command value LCMD is set to the lower limit value LC.
When MDLL is less than or equal to MDLL, the lift command value LCMD may be zero. In this case, the QCMD search value in S20 also becomes zero, and the calculation in S26 is divided by zero, and the calculation becomes impossible.
However, by holding the previous value as described above,
There is no danger that the calculation will not be possible. Although the lower limit LCMDLL is a minute value, it may be zero.

Then, the program proceeds to S34, in which the map search value of the basic exhaust gas recirculation rate correction coefficient KEGRMAP (searched in S14) is replaced with the previous search value KEGRMAPn-1. this is,
In the operating state in which the lift command value LCMD searched in S12 is determined to be equal to or lower than the lower limit value, the basic exhaust gas recirculation rate correction coefficient KEGRMAP searched in S14 is set to 1 in the characteristic expected in this embodiment. , S24 in the calculation in step S24.

In this embodiment, as described above, based on the detected engine speed and engine load, for example, the intake pressure and the operating state of the exhaust gas recirculation valve, the net exhaust gas flowing into the combustion chamber through the exhaust gas recirculation valve is determined. The recirculation rate is calculated for each calculation cycle, and the fuel injection correction coefficient is sequentially calculated and stored for each calculation cycle based on the recirculation rate. In addition, there is no waste until exhaust gas passes through the exhaust recirculation valve and flows into the combustion chamber. The time is calculated, the calculated value of the calculation cycle corresponding to the dead time is selected, and the calculated value is regarded as the fuel injection correction coefficient in the current calculation cycle, so that complicated calculations and uncertain calculation elements are reduced as much as possible. This makes it possible to accurately determine the recirculation rate of the exhaust gas flowing into the combustion chamber and accurately correct the fuel injection amount, with a simple configuration.

Further, paying attention to the flow rate characteristics of the exhaust gas recirculation valve, and estimating the net recirculation rate flowing into the engine combustion chamber, focusing on the fact that the deviation between the transient recirculation rate and the steady-state recirculation rate is the gas amount ratio. With this configuration, the behavior of the exhaust gas can be accurately grasped with a simple configuration. Further, since the gas amount ratio is used, the influence of the exhaust temperature and the exhaust pressure on the gas amount can be absorbed to a considerable extent, and in that sense, the estimation accuracy is improved.

FIG. 11 is a flow chart similar to FIG. 7, showing a second embodiment of the present invention.

A description will be given focusing on the differences from the first embodiment. In S200, S26 in the flowchart of FIG.
Is stored in the ring buffer.
Then, a dead time τ is retrieved in S202, a corresponding net recirculation rate (this is referred to as a “true recirculation rate”) is read out in S204, a fuel injection correction coefficient KEGRN is calculated therefrom, and a fuel injection amount is corrected in S206. .

As described above, according to the second embodiment, the exhaust gas flowing through the exhaust gas recirculation valve and flowing into the combustion chamber from the detected engine speed and the engine load, for example, the intake pressure and the operating state of the exhaust gas recirculation valve. Is calculated and stored for each calculation cycle, and the dead time until exhaust gas passes through the exhaust gas recirculation valve and flows into the combustion chamber is calculated, and the calculated value of the calculation cycle corresponding to the dead time is calculated. Is selected, and it is regarded as the exhaust gas recirculation rate that truly flows into the combustion chamber in the current calculation cycle, so that complicated calculations and uncertain calculation elements can be reduced as much as possible, and the configuration is simple. However, the recirculation rate of the exhaust gas flowing into the combustion chamber can be accurately determined.

FIG. 12 shows a third embodiment of the present invention.
8 is a flowchart similar to FIG. 7.

The following description focuses on the differences from the first embodiment. The flow proceeds from S300 to S302 to S304, where the ring buffer is searched from a predetermined dead time (for example, τ = 12), and the fuel injection used this time is executed. Correction coefficient KEGR
Search for N. That is, except for the point that the dead time is a fixed value, the remaining configuration and effect are not different from those of the first embodiment. Here, the dead time has a different value for each engine depending on the distance between the exhaust gas recirculation valve and the combustion chamber and the like, but is determined in advance through experiments.

In the third embodiment, the net recirculation rate may be stored in the ring buffer instead of the fuel injection correction coefficient KEGRN, as in the second embodiment.

FIG. 13 is a flow chart showing a fourth embodiment of the present invention, and is a flow chart showing a calculation operation of the basic ignition timing θMAP.

First, in step S400, a θMAP map for non-recirculation of exhaust gas is retrieved from the current engine speed NE and intake pressure PBA to obtain a basic ignition timing for non-recirculation of exhaust gas (hereinafter referred to as “θMAPO”). Then, the routine proceeds to S402, where a θMAP map for exhaust gas recirculation is retrieved from the same parameters to obtain a basic ignition timing for exhaust gas recirculation (hereinafter referred to as “θMAPT”). FIG.
Shows the characteristics of the above-described θMAP map.

Next, the routine proceeds to S404, where the basic ignition timing θMAP is calculated from the equation shown. According to the equation shown, the fuel injection correction coefficient KEGRN = 1 when the exhaust gas is not recirculated, so that the basic ignition timing θMAP becomes the basic ignition timing θMAPO when the exhaust gas is not recirculated. On the other hand, the fuel injection correction coefficient KEGR
When N and the steady state fuel injection correction coefficient KEGRMAP match, the basic ignition timing θMAP becomes the basic ignition timing θMAPT during recirculation. Also, the fuel injection correction coefficient KEG
In the state where RN does not coincide with the steady-state fuel injection correction coefficient KEGRMAP, the basic ignition timing θMAP is linearly interpolated between the non-recirculation basic ignition timing θMAPO and the recirculation basic ignition timing θMAPT according to the ratio between the two. (At this time, even if the actual basic ignition timing θMAP shows the behavior shown by the broken line, there is no problem because the difference from the straight line is very small.)

Here, the fuel injection correction coefficient KEGRN is
The first embodiment shown in FIG. 7, the second embodiment shown in FIG. 11,
Alternatively, a value obtained in consideration of the dead time described in the third embodiment shown in FIG. 12 is used. In particular, the second type shown in FIG.
In the case of the embodiment, the net reflux rate may be bufferably searchable instead of (1-KEGRN).

Further, the steady-state fuel injection correction coefficient KEGR
The MAP corresponds to the first embodiment shown in FIG. 7, the second embodiment shown in FIG. 11, or the third embodiment shown in FIG. 12, which buffers the fuel injection correction coefficient KEGRN and the net recirculation rate. And buffer them at the same time. Further, according to the first embodiment shown in FIG. 7 and the third embodiment shown in FIG. 12, (1-KEGRN) / (1
-KEGRMAP) to obtain the fuel injection correction coefficient KE
Obviously, buffering may be performed similarly to GRN.

The steady-state fuel injection correction coefficient KEGR
The MAP may more easily use the current value obtained in the flow chart of FIG. 2 of the first embodiment.
-KEGRN) / (1-KEGRMAP) is 1.0
Is exceeded, it must be limited to 1.0 so that the ignition timing of the calculated value θMAP does not exceed the basic ignition timing θMAPT during recirculation in the advance direction.

In the fourth embodiment, as described above, the basic ignition timing is determined using the exhaust gas recirculation valve and the fuel injection correction coefficient KEGRN calculated according to the delay of the recirculated gas flow. Is performed, the ignition timing can be accurately controlled to a desired value. The basic ignition timing is output after correction based on water temperature, intake air temperature, and the like. In the above description, the fuel injection correction coefficient KE
Although the basic ignition timing is directly determined using GRN or the like, the separately determined basic ignition timing is used as the fuel injection correction coefficient KEGRN.
The correction may be performed by using such a method.

In the above description, the exhaust gas recirculation rate or the fuel injection correction coefficient is stored and selected according to the dead time. However, the engine required to calculate the exhaust gas recirculation rate or the fuel injection correction coefficient is used. Parameters such as the number of revolutions may be stored, selected according to the dead time, and the exhaust gas recirculation rate or the fuel injection correction coefficient may be calculated based on the selected value.

Further, in the above, S10 and S2 in FIG.
Although the atmospheric pressure is used in 0, S22, etc., an exhaust pressure may be used instead.

Further, in the above, the values LCMD, KEG
Although RMAP, QCMD, and QACT have been set as map values, they may be calculated each time.

Further, in the above description, the exhaust gas recirculation valve is of a negative pressure type, but may be of an electric type.

Further, although the intake pressure is used as a parameter indicating the engine load, the intake air amount, the throttle opening and the like may be used.

[0089]

According to the first aspect, complicated calculations and uncertain calculation elements can be reduced as much as possible, and the recirculation rate of the exhaust gas flowing into the combustion chamber can be accurately determined with a simple configuration. Can be found well.

Further, since the behavior of the exhaust gas recirculation gas is grasped from the flow characteristics of the exhaust gas recirculation valve, complicated calculations and uncertain calculation elements can be reduced as much as possible. It is possible to accurately estimate the net exhaust gas recirculation rate sucked into the combustion chamber.

According to the second aspect of the present invention, since the dead time is determined according to the operating state of the internal combustion engine, the recirculation rate of the exhaust gas flowing into the combustion chamber can be determined more accurately. .

According to the third aspect , complicated calculations and uncertain calculation elements can be reduced as much as possible, and the net exhaust gas recirculation rate actually sucked into the combustion chamber can be accurately determined with a simple configuration. A good estimation can be made, and the fuel injection amount can be appropriately corrected based on the estimation.

According to the fourth aspect , complicated calculations and uncertain calculation elements can be reduced as much as possible, and the net exhaust gas recirculation rate actually sucked into the combustion chamber can be accurately determined with a simple configuration. The ignition timing can be estimated well, and the ignition timing can be appropriately corrected based on the estimation.

According to the fifth aspect , the recirculation rate of the exhaust gas flowing into the combustion chamber or the fuel injection correction coefficient can be obtained more easily.

[Brief description of the drawings]

FIG. 1 is an overall block diagram showing an exhaust gas recirculation rate estimating apparatus for an internal combustion engine according to the present invention.

FIG. 2 is a flowchart showing an operation of the exhaust gas recirculation rate estimating apparatus of FIG. 1;

FIG. 3 is an explanatory diagram showing a basic algorithm for estimating the exhaust gas recirculation rate according to the present invention, and is an explanatory diagram showing characteristics of a gas amount with respect to a lift amount of the exhaust gas recirculation ratio used in the calculation of the flowchart of FIG.

FIG. 4 is an explanatory diagram showing delay of an actual lift and recirculation gas with respect to a lift command value of an exhaust gas recirculation valve.

FIG. 5 is an explanatory diagram showing map characteristics of an exhaust gas recirculation rate correction coefficient (basic exhaust gas recirculation rate correction coefficient) in a steady state used in the calculation of the flow chart of FIG. 2;

FIG. 6 is an explanatory diagram showing a map characteristic of a lift command value used in the calculation of the flow chart of FIG. 2;

FIG. 7 is a subroutine flowchart showing a calculation operation of a fuel injection correction coefficient in the flowchart of FIG. 2;

FIG. 8 is an explanatory diagram showing a configuration of a ring buffer used in the operation of the flow chart of FIG. 7;

FIG. 9 is an explanatory diagram showing a map characteristic of a dead time τ used in the operation of the flow chart of FIG. 7;

FIG. 10 is a timing chart for explaining the operation of the flow chart of FIG. 7;

FIG. 11 is a flow chart similar to FIG. 7, showing a second embodiment of the present invention.

FIG. 12 is a flow chart similar to FIG. 7, showing a third embodiment of the present invention.

FIG. 13 is a flowchart showing a fourth embodiment of the present invention.

FIG. 14 is an explanatory diagram showing characteristics of a θMAP map used in the operation of the flow chart of FIG. 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine main body 2 Intake pipe 5 Electronic control unit (ECU) 7 Absolute pressure sensor 10 Crank angle sensor 16 Atmospheric pressure sensor 18 Exhaust recirculation passage 19 Exhaust recirculation valve 25 Exhaust recirculation mechanism

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yusuke Hasegawa 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-5-118246 (JP, A) 6-101575 (JP, A) JP-A-59-74364 (JP, A) JP-A-61-81555 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 25/07 550 F02M 25/07 570 F02D 41/02 301 F02D 41/04 330 F02P 5/15

Claims (5)

(57) [Claims] And 1. A exhaust gas recirculation passage for recirculating at least a portion of connecting the exhaust passage of the internal combustion engine intake passage exhaust gas into the intake passage, and an exhaust gas recirculation valve for opening and closing the exhaust gas recirculation passage An internal combustion engine comprising: a. Operating state detecting means for detecting an operating state of the internal combustion engine including at least the engine speed and the engine load at every predetermined detection cycle; b. Exhaust gas recirculation valve operation state detection means for detecting an operation state of the exhaust gas recirculation valve at each of the predetermined detection cycles; c. Obtains the dead time until the exhaust gas flows into the combustion chamber through the exhaust gas recirculation valve, before the detection period corresponding to the dead time from the detected operating state and the operating state of the EGR valve, the exhaust Exhaust gas recirculation rate calculating means for calculating a recirculation rate of exhaust gas flowing into the combustion chamber through the recirculation valve; and d. Rutotomoni equipped with exhaust gas recirculation rate determining means regarded as recirculation ratio of exhaust gas flowing into the exhaust gas recirculation rate the calculated combustion chamber of the internal combustion engine, said exhaust gas recirculation rate calculating means, e. Basic exhaust return from at least engine speed and engine load
Basic exhaust gas recirculation rate determining means for determining the flow rate; f . The exhaust gas recirculation is performed based on the flow characteristics of the exhaust gas recirculation valve.
It passes through the exhaust gas recirculation valve depending on the opening area detection value of the valve
First estimating means for estimating an exhaust gas amount, g . The exhaust gas recirculation is performed based on the flow characteristics of the exhaust gas recirculation valve.
It passes through the exhaust gas recirculation valve depending on the opening area command value of the valve
Second estimating means for estimating the exhaust gas amount, and h . Exhaust gas amount estimated by the first and second estimation means
Of the basic exhaust gas recirculation rate according to the obtained ratio.
To correct the exhaust gas flowing into the combustion chamber of the internal combustion engine .
Exhaust gas recirculation rate estimating apparatus of the internal combustion engine you characterized in that it consists of calculating means for calculating a recirculation rate. Wherein said dead time is the exhaust gas recirculation rate estimation apparatus for an internal combustion engine according to claim 1 Kouki mounting, characterized in that determined in accordance with the operation state of the internal combustion engine. 3. The exhaust gas recirculation rate determining means includes a correction coefficient calculating means for calculating a correction coefficient for correcting a fuel injection amount to be supplied to a combustion chamber of the internal combustion engine in accordance with the exhaust gas recirculation rate. exhaust gas recirculation rate estimating apparatus according to claim 1, wherein or 2 Koki mounting of an internal combustion engine according to. Wherein said exhaust gas recirculation rate determining means 3 from claim 1, wherein, characterized in that it comprises a correction coefficient calculating means for calculating a correction coefficient for correcting the ignition timing of the internal combustion engine in accordance with the exhaust gas recirculation rate Item 6. An exhaust gas recirculation rate estimating device for an internal combustion engine according to any one of the above items . 5. The exhaust gas recirculation rate determining means includes a storage means for sequentially storing at least one of an exhaust gas recirculation rate and a correction coefficient which are calculated in advance in each calculation cycle synchronized with the predetermined detection cycle. claim 1, wherein the selecting at least one of the exhaust gas recirculation rate and the correction coefficient stored in the storage means in accordance with the time
Item 5. The exhaust gas recirculation rate estimating device for an internal combustion engine according to any one of Items 4 to 4 .