JP3971017B2 - Control method for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling an internal combustion engine.
[0002]
[Prior art]
As a conventional method for controlling an internal combustion engine, particularly a torque control method, for example, a technique described in Japanese Patent Application No. 9-38773 is known.
In such a conventional engine torque control method, as shown in FIG. 13, a target torque equivalent value is calculated from the actually detected accelerator opening APS and engine speed Ne, and these are calculated as a basic intake air amount (a certain reference air amount). The target intake air amount TTP is calculated by multiplying them by the target equivalent ratio TFBYA00, and the target throttle valve opening TVO is calculated therefrom.
[0003]
[Problems to be solved by the invention]
However, in a general internal combustion engine, the relationship between the throttle valve opening TVO and the cylinder intake air amount is not a linear function as shown in FIG. In contrast, the change in the cylinder intake air amount is small in the region where the throttle valve opening TVO is large. Therefore, if ultra lean combustion or the like is performed up to a region where the change in the cylinder intake air amount with respect to the change in the throttle valve opening TVO is small, the throttle valve opening TVO becomes smaller than the basic intake air amount TTPST as shown in FIG. As a result, there is a problem in drivability such as torque fluctuation.
The present invention has been made paying attention to such a conventional problem, and provides a threshold value for the target intake air amount TTP, and based on a comparison result between the target intake air amount TTP and the threshold value TTPSL, An object of the present invention is to solve the above problems by not performing ultra lean combustion or clamping the target intake air amount TTP.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is directed to an internal combustion engine having an electronically controlled throttle valve capable of electronically controlling a throttle valve opening, and a target intake air amount is determined from an accelerator opening and an engine speed. A target intake air amount calculation unit for calculating, a target equivalent ratio calculation unit for calculating a target equivalent ratio from the accelerator opening and the engine speed, and a second target intake air amount by dividing the target intake air amount by the target equivalent ratio. A second target intake air amount calculation unit that calculates a threshold value of a second target intake air amount that reduces a change in the cylinder intake air amount with respect to a change in the throttle valve opening. A second target intake air amount comparison unit that compares the threshold value of the second target intake air amount with the second target intake air amount, and a second target intake air amount based on the comparison result; 2 Beyond the target intake air volume threshold The third target intake air amount is set as the second target intake air amount if the second target intake air amount is set to the third target intake air amount and the second target intake air amount is smaller than the second target intake air amount threshold. A third target intake air amount calculation unit that calculates an air amount; and a target throttle valve opening calculation unit that calculates a target throttle valve opening degree from the third target intake air amount and the engine speed. To do.
According to the second aspect of the present invention, a target engine generated torque calculation unit for calculating a target engine generated torque from the accelerator opening and the engine speed, and a target intake air amount at the stoichiometric air-fuel ratio by the target engine generated torque and the engine speed. A target intake air amount calculation unit for calculating the target equivalent air ratio, a target equivalent ratio calculation unit for calculating a target equivalent ratio based on the target engine generation torque and the engine speed, and a second target by dividing the target intake air amount by the target equivalent ratio. A second target intake air amount calculation unit for calculating the intake air amount, and a second target intake air amount for calculating a threshold value of the second target intake air amount in which the change in the cylinder intake air amount with respect to the change in the throttle valve opening is reduced . the amount of the threshold value calculation unit, and the target equivalent ratio operating section second target intake air amount is at greater than the second target intake air amount threshold to avoid selecting a target equivalent ratio for the stratified The second target intake air amount and the engine speed, characterized by comprising the target throttle valve opening calculating section target throttle valve opening degree is calculated, the.
[0005]
[Action]
As outlined above, when the target intake air amount TTP exceeds the target intake air amount threshold value TTPSL so that the ultra lean combustion is not performed in the region where the change in the cylinder intake air amount with respect to the change in the throttle valve opening is small, The target equivalent air ratio TTFYA00 to be selected is switched to that corresponding to the theoretical air-fuel ratio or that of normal lean combustion, or the target intake air amount TTP is set to the threshold value TTPSL, so that the target intake air intake amount TTP is finely adjusted. Good drivability is achieved without excessively reflecting the opening.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of an engine system according to the first embodiment.
This engine system is a so-called engine electronic control system, and the engine control unit 1 is commensurate with the intake air amount based on the intake air amount measured by the air flow meter 2 and the engine speed measured by the crank angle sensor 3. An ignition timing corresponding to the fuel amount, the engine load and the engine speed is calculated, the injector 4 is driven to supply the fuel amount, and the spark plug 5 is ignited in accordance with the ignition timing. Further, the intake system is equipped with an electronically controlled throttle valve 6 that can be electronically controlled in opening and driven by a motor 6a, and can control the amount of intake air. In addition, 7 is a water temperature sensor, 8 is an exhaust sensor, and 9 is an accelerator sensor.
[0007]
FIG. 2 is a functional configuration diagram of the first embodiment.
Hereinafter, the first embodiment will be described with reference to the flowcharts of FIGS.
In the target intake air amount calculation unit, first, the accelerator opening APS detected by the accelerator sensor 9 is read in step 1, and the engine speed is determined based on the crank angle signal detected by the crank angle sensor 3 in step 2. Ne is detected. From these, in step 3, the target intake air amount TTPST at the stoichiometric air-fuel ratio is calculated based on FIG. As the target intake air amount TTPST, a basic fuel injection pulse width corresponding to the intake air amount for each intake stroke is used. Of course, any one of the intake air amount per intake stroke, the intake air amount per unit time, the fuel amount corresponding to these intake air amounts at the stoichiometric air-fuel ratio, and the ratio to the maximum intake air amount at the current engine speed. It may be used.
[0008]
In step 4, the target equivalent ratio calculation unit calculates the target equivalent ratio TFBYA00 from the accelerator opening APS and the engine speed Ne based on FIG. The target equivalent ratio TFBYA00 may be changed according to the cooling water temperature detected by the water temperature sensor 7, for example.
In step 5, the target intake air amount calculation unit calculates the second target intake air amount TTP by dividing the target intake air amount TTPST by the target equivalent ratio TFBYA00.
In step 6, the threshold value TTPSL of the second target intake air amount TTP stored in advance is read. The threshold value TTPSL for the second target intake air amount may be changed according to the engine speed Ne as shown in FIG. 6, for example.
[0009]
In step 7, the second target intake air amount TTP is compared with the second target intake air amount threshold value TTPSL, and if the second target intake air amount TTP is larger than the second target intake air amount threshold value TTPSL, step Proceeding to FIG. 8, the second target intake air amount threshold value TTPSL is substituted for the third target intake air amount TTPGAS, and TTSLLL is substituted for the second target intake air amount threshold value TTPSL. On the other hand, if the second target intake air amount TTP is equal to or smaller than the second target intake air amount threshold value TTPSL, the routine proceeds to step 9 where the second target intake air amount TTP is substituted for the third target intake air amount TTPGAS. TTPSLH is substituted for the threshold TTPSL of the second target intake air amount.
[0010]
TTPSLL and TTPSLH are hysteresis for preventing hunting in the determination of the threshold value TTPSL of the second target intake air amount.
In step 10, the target total opening area TAAIR of the throttle valve is calculated from the third target intake air amount TTPGAS and the engine speed Ne.
[0011]
In step 11, the target throttle valve opening degree TTVO is calculated from the target total opening area TAAIR. The relationship between the target total opening area TAAIR and the target throttle valve opening degree TTVO can be easily set with reference to the drawings. The target throttle valve opening TTVO is a target throttle valve opening for supplying a second target intake air amount TTP that is a target intake air amount at a predetermined air-fuel ratio.
The electronically controlled throttle valve 6 is driven so that the throttle valve opening TVO becomes the target throttle valve opening TTVO.
[0012]
The intake air metering unit receives the intake air amount Qa per unit time measured by the air flow meter 2 and the engine speed Ne, and the basic fuel injection pulse width TP corresponding to the intake air amount per intake stroke at the stoichiometric air-fuel ratio. Is calculated.
The fuel injection pulse width TI is calculated by adding the invalid fuel pulse width TS corresponding to the battery voltage to the effective fuel injection pulse width TE obtained by multiplying the basic fuel injection pulse width TP by the target equivalent ratio TFBYA00, and the injector 4 is driven.
[0013]
FIG. 7 is a flowchart of the second embodiment.
In the following, the second embodiment will be described.
In step 1, the accelerator opening APS is detected, and in step 2, the engine speed Ne is detected. In step 3, the target engine generated torque TTe is calculated from the map shown in FIG. Here, the target engine generated torque TTe can be substituted with a value designated from the outside, and the target engine generated torque TTe may be a relative value with respect to the maximum torque instead of an absolute value.
[0014]
In step 4, the target engine generated torque TTe and the engine speed Ne are input by the target intake air amount calculation unit, and the target intake air amount TTPST at the theoretical air-fuel ratio is calculated from the map of FIG. As the target intake air amount TTPST, a basic fuel injection pulse width corresponding to the intake air amount for each intake stroke is used. Of course, any of the intake air amount per intake stroke itself, the intake air amount per unit time, the fuel amount corresponding to these intake air amounts at the theoretical air-fuel ratio, and the ratio to the maximum intake air amount at the current engine speed is used. May be.
[0015]
In step 5, the target engine generation torque TTe, the engine speed Ne, the coolant temperature, and the like are input to the target equivalence ratio calculation unit, and whether or not stratified combustion (injecting fuel at the end of the compression stroke) can be performed accordingly, for example. The target equivalent ratio TFBYA00 is calculated in accordance with the determination.
[0016]
In Step 6, the second target intake air amount TTP is calculated by dividing the target intake air amount TTPST by the target equivalent ratio TFBYA00.
In step 7, the threshold value TTPSL of the second target intake air amount TTP stored in advance is read. The threshold value TTPSL of the second target intake air amount TTP may be changed according to, for example, the engine speed Ne.
In step 8, the second target intake air amount TTP and the second target intake air amount threshold value TTPSL are compared, and if the second target intake air amount TTP is greater than the second target intake air amount threshold value TTPSL, Proceeding to step 9, the flag 1 becomes 1, and the target equivalent ratio for stratification is not selected at the next calculation of the target equivalent ratio TFBYA00.
[0017]
Here, the target equivalent ratio calculation unit will be described based on the flowchart of the target equivalent ratio calculation unit of FIG.
In step 5-1, it is determined whether or not the lean operation is possible based on the engine water temperature, the time after startup, the engine speed, the target engine generated torque TTe, and the like. If it is determined that the lean operation is impossible, the routine proceeds to step 5-8, where the stoichiometric target equivalent ratio is selected.
[0018]
If it is determined in step 5-1 that the lean operation is possible, the process proceeds to step 5-2, and it is further determined whether or not the stratified lean operation is possible based on the engine water temperature, the time after start, the engine speed, the target engine generation torque TTe, and the like. If it is determined that the stratified lean operation is impossible, the process proceeds to step 5-6, and a target equivalent ratio for homogeneity is selected. On the other hand, if it is determined that the stratified lean operation is possible, the routine proceeds to step 5-3, where it is determined whether or not the flag 1 set during the previous calculation is 1.
[0019]
If it is determined that the flag 1 is 1, the process proceeds to step 5-4, where it is determined whether both the target intake air amount TTPST and the target equivalent ratio TFBYA00 have changed. This is for preventing the occurrence of hunting of the target equivalent ratio TFBYA00 and the second target intake air amount TTP so that the flag 1 does not become 0 for a certain period of time once the flag 1 becomes 1, and the target intake air amount TTPST And the target equivalence ratio TFBYA00 may change, and a simple elapsed time may be used.
[0020]
If it is determined that both the target intake air amount TTPST and the target equivalent ratio TFBYA00 have not changed, the process proceeds to step 5-6 to select a target equivalent ratio for homogeneity. On the other hand, if it is determined that either the target intake air amount TTPST or the target equivalent ratio TFBYA00 has changed, the process proceeds to step 5-5, flag 1 is set to 0, and the target equivalent ratio for stratification is selected in step 5-7. Is done.
[0021]
The change in both the target intake air amount TTPST and the target equivalence ratio TFBYA00 is used as the return condition, for example, as a result of comparison between the second target intake air amount TTP and the second target intake air amount threshold value TTPSL this time. Even if the intake air amount TTPST is larger than the second target intake air amount threshold value TTPSL and the flag 1 becomes 1, the target equivalent ratio for stratification is not selected at the next calculation of the target equivalent ratio TFBYA00. The calculated target equivalent ratio TFBYA00 becomes larger than this time, and as a result, the next second target intake air amount TTP may be smaller than the second target intake air amount threshold value TTPSL, and this determination may cause hunting. Because there is. Further, a hysteresis is also provided to the threshold value TTPSL of the second target intake air amount to prevent determination hunting.
[0022]
Returning to FIG. 7, the flowchart of the second embodiment will be described again.
In step 10, the target total opening area TAAIR of the throttle valve is calculated from the third target intake air amount TTPGAS and the engine speed Ne.
In step 11, the target throttle valve opening degree TTVO is calculated from the target total opening area TAAIR. The relationship between the target total opening area TAAIR and the target throttle valve opening degree TTVO can be easily set with reference to the drawings. The target throttle valve opening TTVO is a target throttle valve opening for supplying a second target intake air amount TTP that is a target intake air amount at a predetermined air-fuel ratio.
[0023]
The electronically controlled throttle valve 6 is driven so that the throttle valve opening TVO becomes the target throttle valve opening TTVO.
[0024]
The intake air metering unit receives the intake air amount Qa per unit time measured by the air flow meter 2 and the engine speed Ne, and the basic fuel injection pulse width TP corresponding to the intake air amount per intake stroke at the stoichiometric air-fuel ratio. Is calculated.
[0025]
The fuel injection pulse width TI is calculated by adding the invalid fuel pulse width TS corresponding to the battery voltage to the effective fuel injection pulse width TE obtained by multiplying the basic fuel injection pulse width TP by the target equivalence ratio TFBYA00, and the injector 4 is driven. .
[0026]
Next, a series of actions of the embodiment will be described based on FIG. 11. In any of the first and second embodiments, the target intake air amount is set so that the hatched portion of FIG. 12 is not used during stratified lean. Since the threshold value is set, it is possible to avoid fine movement of the target intake air amount and excessive movement of the throttle valve in response to an error as shown in FIG. 11, and to ensure good operability.
[0027]
【The invention's effect】
As explained above, in the region where the change in intake air amount is small relative to the change in throttle valve opening, ultra-lean combustion is not performed. In this region, it is possible to avoid the excessive movement of the throttle valve and to ensure good drivability without impairing the fuel consumption because the effect of improving the fuel efficiency by performing lean combustion is small. I can do it.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an engine system according to the present invention.
FIG. 2 is a functional configuration diagram in the present invention.
FIG. 3 is a flowchart in the first embodiment of the present invention.
FIG. 4 is a target intake air amount map with respect to accelerator opening and engine speed.
FIG. 5 is a target equivalence ratio map with respect to accelerator opening and engine speed.
FIG. 6 is a diagram showing a relationship between an engine speed and a threshold value of a second target intake air amount.
FIG. 7 is a flowchart in the second embodiment of the present invention.
FIG. 8 is a target engine generated torque map with respect to accelerator opening and engine speed.
FIG. 9 is a target intake air amount map with respect to target engine torque and engine speed.
FIG. 10 is a flowchart of a target equivalent ratio calculation unit.
FIG. 11 is a diagram illustrating the operation of the embodiment.
FIG. 12 is a diagram illustrating the operation of the embodiment.
FIG. 13 is a configuration diagram of a conventional engine torque control method.
FIG. 14 is a diagram showing a relationship between a throttle valve opening and a cylinder intake amount of a general internal combustion engine.
FIG. 15 is a diagram showing a relationship between a basic intake air amount and a target intake air amount.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine control unit 2 Air flow meter 3 Crank angle sensor 4 Injector 5 Spark plug 6 Electronically controlled throttle valve 6a Motor 7 Water temperature sensor 8 Exhaust sensor 9 Accelerator sensor

Claims (2)

In an internal combustion engine having an electronically controlled throttle valve capable of electronically controlling the throttle valve opening,
A target intake air amount calculation unit for calculating a target intake air amount from the accelerator opening and the engine speed;
A target equivalent ratio calculation unit for calculating a target equivalent ratio from the accelerator opening and the engine speed;
A second target intake air amount calculation unit for calculating the second target intake air amount by dividing the target intake air amount by the target equivalent ratio;
A second target intake air amount threshold value calculation unit for calculating a threshold value of the second target intake air amount in which the change in the cylinder intake air amount with respect to the change in the throttle valve opening is small ;
A second target intake air amount comparison unit for comparing the threshold value of the second target intake air amount and the second target intake air amount;
Based on the comparison result, if the second target intake air amount is larger than the second target intake air amount threshold, the second target intake air amount is set as the third target intake air amount, and the second target intake air amount is set. A third target intake air amount calculation unit that calculates a third target intake air amount as the second target intake air amount if the air amount is smaller than a threshold value of the second target intake air amount;
A target throttle valve opening calculator for calculating the target throttle valve opening from the third target intake air amount and the engine speed;
A control method for an internal combustion engine, comprising: A target engine generated torque calculation unit for calculating a target engine generated torque from the accelerator opening and the engine speed;
A target intake air amount calculation unit for calculating a target intake air amount at the theoretical air-fuel ratio based on the target engine generated torque and the engine speed;
A target equivalent ratio calculation unit for calculating a target equivalent ratio based on the target engine generation torque and the engine speed;
A second target intake air amount calculation unit for calculating the second target intake air amount by dividing the target intake air amount by the target equivalent ratio;
A second target intake air amount threshold value calculation unit for calculating a threshold value of the second target intake air amount in which the change in the cylinder intake air amount with respect to the change in the throttle valve opening is small ;
A target equivalence ratio operation unit that prevents the target equivalence ratio for stratification from being selected when the second target intake air amount is greater than the threshold value of the second target intake air amount ;
A target throttle valve opening calculator that calculates a target throttle valve opening based on the second target intake air amount and the engine speed;
A control method for an internal combustion engine, comprising:

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