JPH08177582A - Control device for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a control device for an internal combustion engine capable of satisfying different required characteristics for each operating state. [Structure] In S32, it is determined whether or not lean control is being performed, and if lean control is being performed, the latest basic fuel injection is performed when the average value Avtp of the basic fuel injection amount Tp is obtained so as to suppress the air-fuel ratio variation in S33. Fl so that the amount Tp is not reflected so much
If oad (= FloadL) is set to a large value and lean control is not being performed, Fl is set so that the latest basic fuel injection amount Tp is well reflected so that the transient response is prioritized in S34.
Set oad (= FloodR) small. Also, S
When it is determined in 31 that the air-fuel ratio is being switched, S35
And Fload larger than FloadL and FloodR
By setting T, the influence on the combustion stability due to the switching of the target air-fuel ratio is reduced. This makes it possible to satisfy different engine operating characteristics required during lean operation, stoichiometric operation, or switching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly, to stoichiometric control for controlling the air-fuel ratio of engine intake air-fuel mixture to stoichiometric (theoretical air-fuel ratio), and lean air-fuel ratio of engine intake air-fuel mixture. The present invention relates to a control technique for an internal combustion engine capable of satisfying the engine operating characteristics required in various operating states such as lean control for controlling (lean air-fuel ratio), EGR (exhaust gas recirculation) control, non-EGR control, or steady / transient conditions. .

[0002]

2. Description of the Related Art Conventionally, as a stability control technique for an internal combustion engine, there is one disclosed in, for example, Japanese Patent Laid-Open No. 62-60943. This product reduces the fluctuation range of the air-fuel ratio by making the feedback control constants (integral constant and proportional constant) of the air-fuel ratio smaller during lean operation, and stabilizes combustion during lean operation, where misfires are more likely to occur. It aims to secure the sex.

[0003]

However, for example, when operating in the vicinity of the stoichiometric air-fuel ratio, the combustion stability is comparatively high, so there is no problem so much, but the fuel supply amount is originally small as in lean operation. Sometimes, if the measured value of the intake air flow rate or the variation of the basic fuel supply amount obtained from it changes, it will have a relatively large effect on the air-fuel ratio variation. However, there was still a problem that the engine stability during lean operation could not be sufficiently secured. Since the combustion stability is low during the EGR control as well, fluctuations in the air-fuel ratio adversely affect the combustion stability, and therefore there is the same problem as during lean operation.

Further, during the transient operation, the measured value of the intake air flow rate or the fluctuation of the basic fuel supply amount obtained from the measured value of the intake air flow rate is absorbed during the change of the operating state during the transient operation. It is difficult to feel a sense of discomfort even if there are some of these fluctuations, but in steady operation, the driver keeps the accelerator operation constant, and in such a case, it may depend on the measured value of the intake air flow rate or the fluctuation of the basic fuel supply amount obtained from it. Since it is easy for the driver to perceive engine load fluctuations, it is necessary to suppress fluctuations in the measured value of the intake air flow rate during steady operation or fluctuations in the basic fuel supply amount, and consequently fluctuations in the air-fuel ratio.

The present invention has been made in view of the above-mentioned conventional circumstances. For example, a relatively large variation in the air-fuel ratio during lean operation or EGR (exhaust gas recirculation) control has a great influence on engine stability. During operation or during steady operation where the driver is likely to feel uncomfortable, the air-fuel ratio fluctuation is suppressed by changing the intake air flow rate or the calculation process of the basic fuel supply amount calculated based on this, An object of the present invention is to provide a control device for an internal combustion engine that can satisfy different required characteristics for each operating state. It is also an object to further improve the accuracy of the control device and simplify the configuration.

[0006]

Therefore, the control device for an internal combustion engine according to the invention described in claim 1 detects a value related to the engine intake air flow rate as shown in FIG. In the control device of the internal combustion engine that calculates the basic fuel supply amount based on the calculated value and sets the engine operation control amount based on the calculated basic fuel supply amount, the operating state detection that detects the engine operating state According to the means A and the detected engine operating state, the value related to the latest engine intake air flow rate in the setting process of the engine operation control amount or the reflection degree of the latest basic fuel supply amount is changed. And a basic fuel supply amount calculation process changing unit B that changes the calculation process of the basic fuel supply amount.

In the second aspect of the present invention, the basic fuel supply amount calculation process changing means B calculates the basic fuel supply amount based on a value obtained by averaging values related to the engine intake air flow rate. In addition, the weighting of the value related to the latest engine intake air flow rate in the averaging process of the value related to the engine intake air flow rate is configured as a means for changing according to the operating state.

According to the third aspect of the invention, when the basic fuel supply amount calculation process changing means B sets the engine operation control amount based on the value obtained by averaging the basic fuel supply amount, the basic fuel supply amount is changed. The weighting of the latest basic fuel supply amount in the amount averaging process is configured to be changed according to the operating state. In the invention according to claim 4, the value related to the latest engine intake air flow rate or the reflection degree of the latest basic fuel supply amount in the setting process of the engine operation control amount is set to the lean air-fuel ratio operation state or the exhaust gas recirculation control operation. It is configured to be smaller as the state.

According to the fifth aspect of the present invention, a value related to the latest engine intake air flow rate in the process of setting the engine operation control amount or a reflection degree of the latest basic fuel supply amount,
The smaller the air-fuel ratio or the larger the exhaust gas recirculation ratio, the smaller the air-fuel ratio. According to the sixth aspect of the invention, the operating state includes the degree of progress of switching of the operating state between different operating states.

According to a seventh aspect of the present invention, a value relating to the latest engine intake air flow rate in the process of setting the engine operation control amount, or a reflection degree of the latest basic fuel supply amount,
It is configured to be smaller as it approaches the steady operation state.
In the invention described in claim 8, the steady operation state is configured to be an operation state near the road.

[0011]

In the invention according to claim 1 having the above-mentioned structure, the engine operation control amount based on the basic fuel supply amount (for example,
In the process of setting the fuel supply amount, ignition timing, etc.), the basic fuel supply amount is calculated according to the operating state, and the value related to the latest engine intake air flow rate in the setting of the engine operation control amount or the latest value. The degree of reflection of the basic fuel supply amount can be changed so that different required characteristics (for example, engine stability and transient response) can be satisfied for each operating state. This is because, for example, if you want to prioritize engine stability, set the reflection level to a small value,
When it is desired to give priority to the transient response, it can be achieved by setting the reflection degree to be large.

According to the second and third aspects of the present invention, a value related to the latest engine intake air flow rate in the engine control amount setting process based on the basic fuel supply amount or a simple method can be reliably performed. It is possible to change the reflection degree of the latest basic fuel supply amount. According to the fourth aspect of the present invention, during the lean air-fuel ratio operation or the EGR control operation, a value related to the latest engine intake air flow rate or the latest basic value in the processing for setting the engine operation control amount based on the basic fuel supply amount. By reducing the degree of reflection of the fuel supply amount, the fluctuation of the air-fuel ratio is reduced to improve the combustion stability, and thus the engine stability. In addition, during stoichiometric operation, non-EGR control operation, and the like, by increasing the reflection degree, it becomes possible to improve responsiveness during transient operation.

According to a fifth aspect of the present invention, the degree of reflection is adjusted so that the air-fuel ratio becomes leaner or the exhaust gas recirculation rate (EG
By making it smaller as the R amount / intake air flow rate) becomes higher, it is possible to cope with the tendency that the combustion stability deteriorates as the air-fuel ratio becomes leaner or the exhaust gas recirculation ratio becomes higher. Become. In the invention according to claim 6, the operating state is configured to include the progress degree of switching of the operating state between different operating states, and it is possible to meet different required characteristics depending on the progress degree of switching. I chose

According to the seventh aspect of the present invention, the reflection degree is configured to be smaller as it approaches a steady operation state, and unnecessary load fluctuations during steady operation are suppressed (under lean air-fuel ratio, EGR control. Improvement of combustion stability during operation)
On the other hand, while ensuring the responsiveness during transient operation. In the invention according to claim 8, the steady operation state is set to an operation state near the road load, and the steady operation state is detected (in other words, the presence / absence determination of the driver's intention to accelerate / decelerate). The simple structure enables quick and highly accurate detection, and the reflection degree can be changed with high responsiveness in accordance with the driver's intention.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 2 showing the overall configuration of the first embodiment of the present invention, the intake air flow rate Q is set in the intake passage 12 of the engine 1.
A throttle valve for controlling the intake air flow rate Q is provided in conjunction with an air flow meter 2 for detecting the above, and an accelerator pedal, and an electromagnetic fuel injection valve 6 is provided for each cylinder in a downstream manifold portion. Further, a crank angle sensor 3 is provided which detects a crank position and an engine rotation speed N by generating a pulse signal at every predetermined angle in synchronization with the rotation of the crankshaft and the camshaft of the engine 1.

The fuel injection valve 6 is controlled by a drive pulse signal set as described later in the control unit 5 including an input / output interface, an A / D converter, a ROM, a RAM, a CPU and the like. The valve is driven to open, fuel is pressure-fed from a fuel pump (not shown), and fuel is injected and supplied at a predetermined pressure controlled by a pressure regulator (not shown). It should be noted that the air-fuel mixture sucked into the combustion chamber of the engine 1 is ignited and burned by an ignition plug 4 provided facing the combustion chamber of each cylinder.
Based on the drive signal from the control unit 5, ignition is performed by receiving a high voltage from the ignition coil 7 at an ignition timing preset according to the operating state (basic fuel injection amount, engine speed, etc.).

A water temperature sensor 8 for detecting the cooling water temperature Tw in the cooling jacket of the engine 1 is also provided. In the exhaust passage 11, an air-fuel ratio sensor 17 for detecting the air-fuel ratio by detecting the oxygen concentration in the exhaust is provided in the vicinity of the manifold collecting portion, and a catalyst container 14 is provided on the downstream side thereof. Inside the catalyst container 14, a lean NOx catalyst 15 as a first catalyst of the present invention and a three-way catalyst 16 as a second catalyst of the present invention are held.
The air-fuel ratio sensor 17 outputs a voltage according to the oxygen concentration in the exhaust gas to the control unit 5, and the control unit 5 can detect the air-fuel ratio based on this voltage. In this embodiment, the air-fuel ratio sensor 17
May be a sensor having a linear characteristic with respect to the air-fuel ratio, or may be a sensor that determines rich / lean.

By the way, an EGR (Exhaust gas recirculation) valve 10 having a step motor 9 (or a proportional solenoid) or the like and capable of changing a lift amount (valve opening amount)
And an exhaust gas recirculation passage 13 that connects the exhaust system and the intake system via the EGR valve 10. EG
The R valve 10 is drive-controlled by a drive signal from the control unit 5, and is set to a lift amount such that an EGR rate (EGR amount / intake air flow rate) set in advance according to an operating state can be obtained.

The control unit 5 functioning as the operating condition detecting means and the basic fuel supply amount calculation processing changing means of the present invention receives input signals from the various sensors,
The flowcharts of FIGS. 3 to 6 are executed. Note that FIG.
The flowchart of FIG. 10 is a flowchart for the arithmetic processing of the average basic fuel injection amount Avtp, which is the point of the present invention. In the present embodiment, the setting control of the control amount (fuel injection amount in the present embodiment) of the internal combustion engine in which the stoichiometric operation and the lean operation are switched under a predetermined operating condition will be described.

The flowcharts of FIGS. 3 to 10 will be described below in order. The flowchart of FIG. 3 shows a routine for setting the fuel-air ratio during lean operation. This flow is executed in synchronization with a rotation signal or a reference signal (so-called reference signal) for each cylinder. Step (in the figure,
It is written as S. The same applies hereinafter) 1, the target fuel air ratio Td
m1 is set based on a map fuel-air ratio Mdm1 that is set in advance according to operating conditions (engine speed, load, etc.). The map fuel-air ratio Mdm1 is shown in FIG.
It is set by executing the flow chart of.

From step 2 onward, the damper for switching the fuel-air ratio is operated. This is because a gentle change in the air-fuel ratio suppresses a sudden change in torque and suppresses deterioration of drivability. First, in step 2, the currently set fuel-air ratio correction coefficient Dm1 and Tdm1 obtained previously are calculated.
If Dm1 ≧ Tdm1, the process proceeds to step 5, and Dm1l (fuel-air ratio change speed, lean side) is subtracted from the held Dm1 to obtain a new Dm.
Ask for 1. Then, in step 6, Dm1 becomes T
The flow is ended by limiting Dm1 so that it does not become less than dm1.

If Dm1 <Tdm1, the process proceeds to step 3 to add a new Dm1 by adding Dm1r (fuel air ratio change speed, rich side) to the held Dm1.
Ask for 1. Then, the process proceeds to step 4, where Dm1 is T
The flow is ended by giving a restriction to Dm1 so as not to exceed dm1. The fuel-air ratio correction coefficient Dm1 thus obtained is used in the calculation of the fuel injection amount described later. FIG. 4 is a background job (BGJ) executed in the lean-running internal combustion engine, and the map fuel air ratio Mdm.
6 is a flowchart for calculating 1.

In step 11, the lean condition is judged. The determination is to set a region in which lean operation is desired from the requirements of fuel economy, exhaust gas, and drivability, and determine whether or not the current operating condition is within that range, but detailed description is omitted here. To do. If it is the lean condition, the routine proceeds to step 13, where the lean map fuel-air ratio MDMLL set in advance according to the operating condition (engine speed, load, etc.) is searched, and the MDMLL is used as the map fuel-air ratio Mdm1. Then, this flow ends.

On the other hand, if it is not the lean condition, step 14
And proceeds to search the stoichiometric map fuel-air ratio MDMLS that is set in advance according to operating conditions (engine speed, load, etc.), and finds the MDMLS in question in the map fuel-air ratio Mdm1.
Then, this flow ends. In this way,
The map fuel-air ratio Mdm1 is set according to the operating conditions. Then, the subsequent Tdm1, Dm1, Tfb
Prepare for the calculation of ya and Ti.

Next, the flowchart of FIG. 5 will be described. The flow is a flow for calculating the fuel injection amount (injection pulse width) Ti by using the fuel-air ratio correction coefficient Dm1 and outputting the fuel injection amount Ti to the fuel injection valve 6 in the internal combustion engine performing the lean operation. In step 21, the fuel-air ratio correction coefficient D
Using m1, the target fuel air ratio Tfbya (= Dm1 + Kt
w + Kas + ..., Ktw is a water temperature correction coefficient, and Kas is an increase amount after starting).

In step 22, the output value of the air flow meter 2 is A / D converted and linearized to obtain the intake air flow rate Q. In step 23, the average value Avtp of the basic fuel injection amount Tp is obtained. The calculation of the average value Avtp will be described in detail later. In step 24, the final fuel injection amount Ti (= Avtp × Tfbya × Ktr ×
(Α + αm) + Ts, Ktr is a transient correction coefficient, α is an air-fuel ratio feedback correction coefficient, αm is an air-fuel ratio learning correction coefficient, and Ts is an invalid pulse width).

In step 25, fuel cut determination is performed. If it is the fuel cut condition, proceed to step 28 and Ts
To the output register, otherwise step
Proceeding to 27, Ti is stored in the output register to prepare for injection at a predetermined injection timing. The target fuel-air ratio Tfbya and the fuel injection amount T in step 21 are set.
It may be the same as the conventional one except that the average value Avtp is used for the calculation of i.

By the way, the above air-fuel ratio feedback correction coefficient α is used to correct the product error of the fuel injection valve 6 and the like.
It is increased / decreased by proportional-integral (PI) control or the like based on the output of the air-fuel ratio sensor 17, whereby the air-fuel ratio of the combustion mixture can be feedback-controlled to the target air-fuel ratio. Further, the air-fuel ratio learning correction coefficient αm updates and stores the deviation of the air-fuel ratio feedback correction coefficient α from the reference value (target convergence value), for example, for each of a plurality of engine operating regions (that is, learning areas). By correcting the basic fuel injection amount Avtp with the air-fuel ratio learning correction coefficient αm, the base air-fuel ratio obtained without the air-fuel ratio feedback correction coefficient α is made to substantially match the target value. It is possible to accelerate the convergence of the actual air-fuel ratio to the target air-fuel ratio in the fuel ratio feedback control. In other words, by combining the air-fuel ratio feedback correction coefficient α and the air-fuel ratio learning correction coefficient αm, it is possible to respond to the correction request of the fuel injection amount which is different for each operating condition with good responsiveness, and to make the actual air-fuel ratio close to the target air-fuel ratio. It is to be able to control.

Next, the flowchart of FIG. 6 will be described. FIG. 6 shows an example of calculating the average value Avtp of the basic fuel injection amount Tp for a predetermined time. Step
At 31, it is determined whether the difference between the target fuel-air ratio Tdm1 and the currently set fuel-air ratio correction coefficient Dm1 is smaller than a predetermined value ε (that is, the degree of progress of air-fuel ratio switching), and the predetermined value is determined. If it is smaller than ε (judging that switching of the air-fuel ratio is over a predetermined value), proceed to step 32, and if it is a predetermined value ε or more (judging that switching of the air-fuel ratio has not progressed too much). Go to step 35.

In step 32, it is judged whether or not the lean condition is satisfied (currently lean operation is being performed). If the lean condition is satisfied, the process proceeds to step 33, and if the lean condition is not satisfied, the process proceeds to step 34. In step 33, the weighted average constant Floa
Let d be a lean weighted average constant FloadL. on the other hand,
In step 34, the weighted average constant FloadS for non-lean (Stoichi) is set as the weighted average constant Fload.

If it is determined in step 31 that the value is equal to or larger than the predetermined value ε and the process proceeds to step 35, the weighted average constant FloadT during the switching of the air-fuel ratio is set as the weighted average constant Fload. Next, at step 36, the basic fuel injection amount Tp (= K × Q / N) is obtained from the intake air flow rate Q. In step 37, the basic fuel injection amount Tp and the weighted average constant Fload
And from the weighted average basic fuel injection amount Avtp
(= Tp / Fload + Avtpn _-1 * (Fload-1) / Fload) is calculated, and this flow is ended.

A obtained by weighted averaging in this way
vtp is used to calculate the final fuel injection amount Ti in step 24 of FIG. Here, the lean weighted average constant FloadL is a non-lean weighted average constant Floa.
The value is set to be larger than dS to stabilize the engine during lean operation, while setting the importance on engine responsiveness during non-lean operation. That is, during lean operation, the change in combustion stability with respect to the change in basic fuel injection amount Tp is more sensitive to stoichiometric operation.
(Or change of intake air flow rate Q) should not be reflected so much in the calculation result of the average basic fuel injection amount Avtp this time. On the other hand, during stoichiometric operation, the change in the basic fuel injection amount Tp (or the intake air flow rate Q) is changed to the average basic fuel this time so that the engine operating state can be made to follow the driver's accelerator depression with good response. Injection amount Av
The result is well reflected in the calculation result of tp.

Further, the weighted average constant F during switching of the air-fuel ratio
The loadT is set to a value larger than the lean weighted average constant FloadL and the non-lean weighted average constant FloadS so as to reduce the difference in the operating state due to the change of the target air-fuel ratio, that is, the influence on the combustion stability. The flowchart of FIG. 7 is a flowchart showing another example of the method of calculating the average basic fuel injection amount Avtp.

In step 41, the currently set value of the fuel-air ratio correction coefficient Dm1 is read. In step 42, D
The weighted average constant Fload is calculated from m1. An example of calculating the weighted average constant Fload from Dm1 is shown in FIG. That is, as Dm1 is smaller (air-fuel ratio is leaner), F
Increase load. This is because the leaner the influence of the air-fuel ratio variation on the combustion stability is (the combustion stability is likely to deteriorate), the change in the basic fuel injection amount Tp (or the intake air flow rate Q) is changed to the average basic fuel this time. Injection amount Av
This is because the calculation result of tp may not be reflected so much. Further, although an exponential (particularly quadratic) functional relationship is given to the relationship between Dm1 and Fload, the engine stability tends to deteriorate exponentially (secondary) function when the air-fuel ratio becomes lean. This is because stabilization of the average basic fuel injection amount Avtp corresponding to this is required.

In step 43, the basic fuel injection amount Tp (= K × Q / N) is obtained from the intake air flow rate Q. Step 44
Then, the basic fuel injection amount Tp and the weighted average constant Fload
From the above, the average basic fuel injection amount Avtp is calculated, and this flow is ended. Thus, Avtp obtained by weighted averaging is used for the calculation of the final fuel injection amount Ti in step 24 of FIG. FIG. 9 is a flowchart showing another example of the method of calculating the average basic fuel injection amount Avtp.

At step 51, the currently set value of the fuel-air ratio correction coefficient Dm1 is read. In step 52, D
A weighted average constant basic value Floadd is calculated from m1.
In the table shown in FIG. 8 above,
Fload is replaced with Fload to obtain the value. In step 53, the basic fuel injection amount Tp is calculated from the intake air flow rate Q.

In step 54, the Fload correction coefficient KFload is calculated based on the basic fuel injection amount Tp and the engine speed N by referring to the map shown in FIG. Figure
10 is a road load line of the vehicle (a line representing the engine load set according to the vehicle speed when the gradient is 0%, that is, a line representing the engine load capable of maintaining the vehicle speed while traveling on a flat road [acceleration becomes 0]) As the load becomes higher and lighter, Flo
The ad correction coefficient KFload is set to be small. That is, at the time of acceleration / deceleration, the engine operating state (that is, the intake air flow rate Q and the basic fuel injection amount Tp) is changed with good followability in accordance with the accelerator operation of the driver, while the load load line (steady operating state ) Is close to
The driver does not change the accelerator operation amount so much, and in such a state, even if the followability of the change in the engine operating state to the accelerator operation is reduced, the driver does not feel uncomfortable, so at the time of lean driving In order to give priority to the combustion stability, the change in the basic fuel injection amount Tp (or the intake air flow rate Q) is not so much reflected in the calculation result of the average basic fuel injection amount Avtp this time. During stoichiometric operation, the responsiveness during acceleration / deceleration can be improved as described above, but during steady state, subtle fluctuations in the basic fuel injection amount Tp (or intake air flow rate Q) can be corrected by the average basic fuel of this time. Since the calculation result of the injection amount Avtp can not be reflected so much, the steady running state can be stably maintained. Therefore, it is possible to suppress the generation of a feeling of strangeness to the driver such as a load change even if the accelerator is kept constant. You will be able to

In step 55, the weighted average constant basic value Fl
The weighted average constant Fload is obtained based on oadd and the Fload correction coefficient KFload. As an example, a case where both are multiplied is shown. In step 56,
The average basic fuel injection amount Avtp is obtained from the basic fuel injection amount Tp and the weighted average constant Fload, and this flow ends.

A obtained by weighted averaging in this way
vtp will be used for the calculation of the final fuel injection amount Ti in step 24 of FIG. In the above embodiment, the basic fuel injection amount Tp is weighted and averaged to obtain the average basic fuel injection amount Avtp. However, the intake air flow rate Q is weighted and averaged, and the average value A is obtained.
vQ (= Q / Fload + AvQ _n-1 x (Fload-1) / Fload)
By using the average basic fuel injection amount Avtp (= K × AvQ /
AvN [AvN is an average value])
The final fuel injection amount Ti may be calculated.

As described above, according to the present embodiment, the basic control amount (basic fuel injection amount) used for the engine operation control (here, the setting of the fuel injection amount Ti) is performed according to the operating states with different target air-fuel ratios. Since the calculation process of Tp or the intake air flow rate Q) is changed, for example, it is possible to ensure both combustion stability during lean operation and transient response during stoichiometric operation. In addition, the basic control amount (basic fuel injection amount T
Since p or the intake air flow rate Q) is changed (corresponding to step 54 in the flowchart of FIG. 9), unnecessary load fluctuations during steady operation are suppressed (combustion during lean operation). (Improvement of stability) and securing of responsiveness at the time of transition can be achieved at the same time.

FIG. 11 shows the Tp fluctuation during the conventional lean control and the average basic fuel injection amount Av during the lean control of this embodiment.
A time chart showing fluctuation of tp (or average intake air flow rate Q) is shown. Further, the effect of this embodiment is shown in FIG. It can be seen from this figure that the combustion stability limit is improved by the present embodiment, and thus a good MBT (Minimu
m Spark Advance for Best Torque) will be obtained (it will be able to greatly delay compared to the conventional), NO
It can be seen that the output torque can be maximized while suppressing x, thereby improving fuel efficiency.

In the first embodiment described above, the case of the internal combustion engine in which the lean operation state and the stoichiometric operation state are switched has been described, but the EGR control,
It can also be applied to an internal combustion engine that switches between non-EGR control. Such a case will be described below as a second embodiment. The overall configuration of the second embodiment is the same as that of the first embodiment, so the description will be omitted.

The flowchart of FIG. 13 shows an EGR rate (lift amount of the EGR valve 10) setting routine when the EGR control is performed. This flow is executed in synchronization with a rotation signal or a reference signal (so-called reference signal) for each cylinder. In step 61, the map EGR rate Megr is set to the target EGR.
Set as the rate Tegr. The map EGR rate Megr is obtained by executing the flowchart of FIG. 14 described later.

After step 62, the damper for switching the EGR rate is operated. This is because a gentle change of the EGR rate suppresses a sudden change in torque and suppresses deterioration of drivability. First, in step 62, EG
The R-ratio correction coefficient Egr is compared with Tegr obtained previously, and if Egr ≧ Tegr, the process proceeds to step 65,
A new Egr is obtained by subtracting Degrd (EGR rate change speed, reduction side) from the held Egr _n-1 . Then, the process proceeds to step 66, where Egr is Tegr
Egr is restricted so that it does not become less than, and the flow is ended.

If Egr <Tegr, the process proceeds to step 63, where Degri is added to the held Egr _n-1 .
A new Egr is obtained by adding (EGR rate change speed, increasing side). Then, proceed to step 64, and Eg
Limit Egr so that r does not exceed Tegr,
End the flow. In this way, the target EGR rate Tegr is increased by gradually increasing or decreasing the EGR rate correction coefficient Egr.
Thus, smooth EGR rate control can be performed.

The flowchart in FIG. 14 is for calculating the map EGR rate Megr in the background job (BGJ) executed in the internal combustion engine that is operating in EGR. At step 71, the current operating condition is EGR.
Judge whether it is a control operation permission condition. The determination can be made based on whether or not there is a current operating condition within the EGR operating region set in advance based on the engine speed N, the engine load Tp, the engine water temperature Tw, and the like.

At step 72, the current operating condition is EGR.
When it is determined that the control operation permission condition is satisfied, the process proceeds to step 73, and when it is determined that it is not, the process proceeds to step 74. In step 73, the MEGR map in which the target EGR rate is set beforehand based on the engine speed N, the engine load Tp, the engine water temperature Tw, etc. is searched, and the search result is the map EGR rate M.
After setting as egr, this flow is finished.

In step 74, since it is not in the EGR region, Megr = 0 is set, and this flow is ended.
Also in this embodiment, the same flow chart as in FIG. 5 described in the first embodiment is executed to calculate the fuel injection amount Ti and output it to the fuel injection valve 6. In addition, the lean control is not performed at the same time, and the EGR
If only control is to be performed, D in step 21
The term of m1 will be omitted.

The flowchart of FIG. 15 shows an example of a method of calculating the average value Avtp of the basic fuel injection amount for a predetermined time in step 23 of FIG. 5 executed in this embodiment. In step 81, the target EGR rate Tegr and
It is determined whether the difference between the currently set EGR rate correction coefficient Egr and a predetermined value ε'is smaller (that is, the degree of EGR rate switching progress). If it is determined that the switching is in progress, the process proceeds to step 82. If it is equal to or larger than the predetermined value ε '(it is determined that the switching of the EGR rate has not progressed yet), the step.
Continue to 85.

In step 82, it is judged whether or not the EGR operating condition is satisfied. If the EGR operating condition is satisfied, the process proceeds to step 83, and if the EGR operating condition is not satisfied, the process proceeds to step 84. In step 83, the weighted average constant Floa
Let d be the weighted average constant FloadL during EGR control. On the other hand, in step 84, the weighted average constant Fl during non-EGR control is set.
Let oadS be the weighted average constant Fload.

If it is determined in step 81 that the value is equal to or greater than the predetermined value ε ', and the process proceeds to step 85, the weighted average constant FloadT during the EGR rate switching is changed to the weighted average constant Fload.
And Next, at step 86, the basic fuel injection amount Tp (= K × Q / N) is obtained from the intake air flow rate Q.

At step 87, the basic fuel injection amount Tp,
Average basic fuel injection amount A from the weighted average constant Fload
vtp (= Tp / Fload + Avtp _n-1 x (Fload-1) / Fload)
Is calculated, and this flow ends. Avtp thus obtained by weighted averaging is used for the calculation of the final fuel injection amount Ti in step 24 of FIG.

Here, the weighted average constant Flo during EGR control
adL is set to a value larger than the weighted average constant FloadS during non-EGR control to stabilize the engine during EGR operation, while setting importance on responsiveness of engine operation during non-EGR operation. That is, during the EGR operation, the change in the combustion stability with respect to the change in the basic fuel injection amount Tp is non-EGR.
Since it is sensitive to driving, the basic fuel injection amount Tp
The change in (or intake air flow rate Q) is not so much reflected in the calculation result of the average basic fuel injection amount Avtp this time (meaning). On the other hand, during non-EGR operation, it is responsive to the driver's accelerator depression. In order to be able to follow the engine operating condition well, the change of the basic fuel injection amount Tp (or the intake air flow rate Q) is changed to the average basic fuel injection amount Avt of this time.
The result of p is often reflected in the calculation result.

The weighted average constant FloadT during the switching of the EGR rate is the weighted average constant Fload during EGR control.
L and a value larger than the weighted average constant FloadS during non-EGR control are set so as to reduce the influence on the combustion stability, that is, the difference in the operating state due to the request to change the target EGR rate. The flowchart of FIG. 16 shows the average basic fuel injection amount A.
It is a flowchart which shows another example of the calculation method of vtp.

In step 91, the currently set EG
The value of the R rate correction coefficient Egr is read. In step 92,
The weighted average constant Fload is calculated from Egr. Egr
An example of calculating the weighted average constant Fload from is shown in FIG. That is, the larger Egr (the larger the EGR rate), the larger Fload. This is because the larger the EGR rate, the greater the influence of the air-fuel ratio fluctuation on the combustion stability (because the combustion stability easily deteriorates). Therefore, the change in the basic fuel injection amount Tp (or the intake air flow rate Q) is This is to prevent the calculation result of the average basic fuel injection amount Avtp from being reflected so much. Further, the relationship between Egr and Fload is given an exponential (particularly quadratic) functional relationship.
This is because it tends to worsen functionally, and stabilization of the average basic fuel injection amount Avtp corresponding to this tends to be required.

A obtained by weighted averaging in this way
vtp is used to calculate the final fuel injection amount Ti in step 24 of FIG. FIG. 18 is a flowchart showing another example of the method of calculating the average basic fuel injection amount Avtp.

At step 101, the currently set E
The value of the GR rate correction coefficient Egr is read. In step 102, the weighted average constant basic value Floadd is calculated from Egr. The weighted average constant basic value Floadd is shown in FIG.
In the table as shown in,
The map is obtained by replacing it with add.

In step 103, the basic fuel injection amount Tp is calculated from the intake air flow rate Q. Step 104, Figure 19
Referring to the map as shown in FIG. 5, the Fload correction coefficient KFl is calculated based on the basic fuel injection amount Tp and the engine rotation speed N.
Ask for oad. Figure 19 shows the road load of the vehicle (R /
As the load becomes higher and lighter than line L), Fl
The setting is such that the od correction coefficient KFload is reduced. That is, at the time of acceleration / deceleration, the engine operating state (that is, the intake air flow rate Q and the basic fuel injection amount Tp) is changed with good followability in accordance with the accelerator operation by the driver, while it is close to the steady operating state. , The driver does not change the accelerator operation amount so much, and in such a state, the driver does not feel uncomfortable even if the followability of the change in the engine operating state with respect to the accelerator operation is reduced. To give priority to stability, the basic fuel injection amount Tp
The change in (or the intake air flow rate Q) is not so much reflected in the calculation result of the average basic fuel injection amount Avtp this time. Furthermore, during non-EGR control, the responsiveness during acceleration / deceleration can be improved, while in the steady state, subtle fluctuations in the basic fuel injection amount Tp (or intake air flow rate Q) can be adjusted to the average basic fuel injection amount Avtp. Since it is possible to prevent the calculation result from being reflected so much, it is possible to stably maintain the steady running state, and thus it is possible to prevent the driver from feeling a sense of discomfort due to load fluctuations even when the accelerator is kept constant.

In step 105, the weighted average constant basic value F
The weighted average constant Fload is obtained based on load and the Fload correction coefficient KFload. As an example, a case where both are multiplied is shown. In step 106, the basic fuel injection amount Tp and the weighted average constant Fload
From the above, the average basic fuel injection amount Avtp is obtained, and this flow is ended.

A obtained by weighted averaging in this way
vtp is used to calculate the final fuel injection amount Ti in step 24 of FIG. As described above, according to the second embodiment, the calculation process of the basic control amount (the basic fuel injection amount Tp or the intake air flow rate Q) used for the engine operation control is changed corresponding to the EGR / non-EGR operation. Therefore, it is possible to achieve both ensuring combustion stability during EGR operation and ensuring transient response during non-EGR operation. Also, the calculation process of the basic control amount used for engine operation control is changed according to the steady / transient operation state (Fig. 18).
Step 104 in the flowchart of FIG. 2) corresponds to suppressing unnecessary load fluctuation during steady operation (improvement of combustion stability during EGR operation) and ensuring responsiveness during transition. it can.

In each of the above embodiments, the lean control and the stoichiometric control are performed, the steady operation state and the transient operation state are performed, or the EGR control is performed and the non-EGR control is performed. Engine operation control (here, fuel injection amount Ti
Although the calculation process of the basic control amount (basic fuel injection amount Tp or intake air flow rate Q) used for setting) is changed, the invention is not limited to this and is used for engine operation control according to other operating conditions. By changing the calculation process of the basic control amount, it is possible to meet different required characteristics (engine stability emphasis, responsiveness emphasis, etc.) for each operating state. For example, in ignition timing control, the basic fuel injection amount T
In the operating state in which the target ignition timing determined from these changes due to p or the change in the intake air flow rate Q, which causes engine hunting and the like, the basic fuel injection amount Tp as in the above embodiment.
Alternatively, if the calculation process of the intake air flow rate Q is changed, engine hunting or the like can be suppressed. Alternatively, when the purge air is diluted during the purge process and the air-fuel ratio of the engine intake air-fuel mixture becomes lean (just before the end of the purge process, etc.), the basic fuel injection amount Tp or the intake amount is increased as in the above embodiment. If the calculation process of the air flow rate Q is changed, the engine stability can be secured. Furthermore, in an operating state in which the detected value of the intake air flow rate Q itself fluctuates due to the influence of intake pulsation, blowby gas, etc., the basic fuel injection amount T as in the above embodiment
If p or the calculation process of the intake air flow rate Q is changed, the air-fuel ratio fluctuation is suppressed, and thus engine stability can be ensured.

In each of the above-described embodiments, the intake air flow rate Q is detected by the air flow meter 2. However, the present invention is not limited to this, and is related to the engine intake air flow rate Q such as the intake pipe pressure and the throttle opening. It can also be applied to the case where the basic fuel injection amount Tp is detected based on the value of Further, in each of the above embodiments, the case where the calculation process of the basic fuel injection amount Tp or the intake air flow rate Q is changed to set the fuel injection amount Ti which is one of the engine operation control amounts has been described. The present invention is not limited to this, and can be applied to a case where a control amount related to engine operation control such as ignition timing setting is set based on the basic fuel injection amount.

[0063]

As described above, according to the first aspect of the invention, the value related to the latest engine intake air flow rate in setting the engine operation control amount or the reflection degree of the latest basic fuel supply amount. By changing, it is possible to satisfy different required characteristics for each operating state. This can be achieved, for example, by setting the reflection degree small when it is desired to give priority to engine stability, and setting the reflection degree large when giving priority to transient response.

According to the second and third aspects of the present invention, the value related to the latest engine intake air flow rate in the process of setting the engine control amount based on the basic fuel supply amount or the value or It is possible to change the reflection degree of the latest basic fuel supply amount. According to the fourth aspect of the present invention, during the lean air-fuel ratio operation or the EGR control operation, it is possible to reduce the air-fuel ratio fluctuation and improve the combustion stability and eventually the engine stability.

According to the fifth aspect of the invention, the air-fuel ratio is reduced by making the reflection degree smaller as the air-fuel ratio becomes leaner or as the exhaust gas recirculation rate (EGR amount / intake air flow rate) becomes higher. It is possible to cope with the tendency that the combustion stability deteriorates as the exhaust gas becomes leaner or the exhaust gas recirculation rate becomes higher. According to the invention described in claim 6, it is possible to meet different required characteristics depending on the degree of progress of the switching of the operating state.

According to the seventh aspect of the present invention, it is possible to suppress unnecessary load fluctuation during steady operation (under lean air-fuel ratio, improve combustion stability during steady operation during EGR control operation). You can According to the invention described in claim 8, the reflection degree can be changed with good responsiveness in correspondence with the driver's intention.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is an overall configuration diagram according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating a fuel-air ratio switching damper control according to the embodiment.

FIG. 4 is a flowchart for explaining a map fuel-air ratio setting routine of the embodiment.

FIG. 5 is a flowchart illustrating a fuel injection amount setting routine of the above embodiment.

FIG. 6 is a flowchart illustrating a routine for setting an average basic fuel injection amount according to the above embodiment.

FIG. 7 is a flowchart illustrating another routine for setting the average basic fuel injection amount according to the above embodiment.

FIG. 8 is a diagram for explaining the relationship between Dm1 and Fload according to the embodiment.

FIG. 9 is a flowchart illustrating another routine for setting the average basic fuel injection amount according to the above embodiment.

FIG. 10 is a diagram showing an example of a KFload map according to the embodiment.

FIG. 11 is a time chart comparing the load fluctuations of the above-described example and the conventional example.

FIG. 12 is a view for explaining the effect of the above embodiment.

FIG. 13 is a flowchart illustrating an EGR rate switching damper control according to a second embodiment.

FIG. 14 is a flowchart illustrating a routine for setting a map EGR rate according to the embodiment.

FIG. 15 is a flowchart illustrating an average basic fuel injection amount setting routine according to the embodiment.

FIG. 16 is a flowchart illustrating another routine for setting the average basic fuel injection amount according to the above embodiment.

FIG. 17 is a diagram for explaining the relationship between the EGR rate and Fload in the same example.

FIG. 18 is a flowchart illustrating another routine for setting the average basic fuel injection amount according to the above embodiment.

FIG. 19 is a diagram showing an example of a KFload map according to the embodiment.

[Explanation of symbols]

 1 Internal Combustion Engine 2 Air Flow Meter 3 Crank Angle Sensor 4 Spark Plug 5 Control Unit 6 Fuel Injection Valve 8 Water Temperature Sensor 17 Air-Fuel Ratio Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02D 45/00 G 312 A

Claims (8)

[Claims] 1. A value related to an engine intake air flow rate is detected,
Calculate the basic fuel supply amount based on the detected value,
In a control device for an internal combustion engine configured to set an engine operation control amount based on the calculated basic fuel supply amount, an operation state detection means for detecting an engine operation state, and an engine operation state detected according to the detected engine operation state. A basic fuel supply amount for changing the calculation process of the basic fuel supply amount so as to change the value related to the latest engine intake air flow rate in the setting process of the engine operation control amount or the reflection degree of the latest basic fuel supply amount. A control device for an internal combustion engine, comprising: a calculation process changing means; 2. The basic fuel supply amount calculation processing changing means,
When the basic fuel supply amount is calculated based on the value obtained by averaging the values related to the engine intake air flow rate, it relates to the latest engine intake air flow rate in the averaging process of the values related to the engine intake air flow rate. The control device for an internal combustion engine according to claim 1, which is a unit that changes weighting of values according to an operating state. 3. The basic fuel supply amount calculation processing changing means,
Means for changing the latest weighting of the basic fuel supply amount in the averaging process of the basic fuel supply amount according to the operating state when the engine operation control amount is set based on the value obtained by averaging the basic fuel supply amount 2. The method according to claim 1, wherein
Alternatively, the control device for the internal combustion engine according to claim 2. 4. The value relating to the latest engine intake air flow rate or the reflection degree of the latest basic fuel supply amount in the engine operation control amount setting processing is made smaller in the lean air-fuel ratio operation state or the exhaust gas recirculation control operation state. The control device for an internal combustion engine according to any one of claims 1 to 3, characterized in that. 5. The smaller the air-fuel ratio or the larger the exhaust gas recirculation rate, the smaller the reflection degree of the latest engine intake air flow rate related value or the latest basic fuel supply amount in the engine operation control amount setting processing. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein: 6. The air-fuel ratio of an internal combustion engine according to claim 1, wherein the operating state includes a degree of progress of switching of operating states between different operating states. Control device. 7. The value relating to the latest engine intake air flow rate or the reflection degree of the latest basic fuel supply amount in the process for setting the engine operation control amount is set to be smaller as it approaches a steady operation state. An air-fuel ratio control device for an internal combustion engine according to any one of claims 1 to 6. 8. The air-fuel ratio control apparatus for an internal combustion engine according to claim 7, wherein the steady operation state is an operation state near a road load.