JPH07269396A - Air-fuel ratio control method of internal combustion engine - Google Patents

Abstract

PURPOSE:To decide an accurate fuel injection amount by deciding a basic injection amount based on the opening of a throttle valve and a rotation number and an increase correction injection amount that is according to a bypass air flow from the detected opening of an air flow control valve and the rotation number, deciding a final fuel injection amount from both. CONSTITUTION:A main basic injection time is decided from an engine rotation number and a throttle opening, and an auxiliary basic injection time is decided from the engine rotation number and an operation duty ratio (S1, 2). Next, a main load correction coefficient is calculated in order to conduct correction by means of load, and a load time correction injection amount is decided from the engine rotation number, and a follower load correction coefficient is decided in opposition to load (S3-5). The main basic injection time is temporarily memorized, and a value that is the auxiliary basic injection time multiplied by the main load correction coefficient is added to the basic injection time and is memorized, and an intake air amount is decided by the sum of the main basic injection time and the auxiliary basic injection time corrected by the main load correction coefficient (S6-7). An injection time is operated by deciding the existence of the intake air amount (S8-9).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention according to claim 1 and claim 2 of the present application (hereinafter referred to as the present invention) is mainly based on the rotational speed of an internal combustion engine for automobiles and the opening of a throttle valve. The present invention relates to an air-fuel ratio control method for determining

[0002]

2. Description of the Related Art Conventionally, as an air-fuel ratio control method of this type, for example, as disclosed in Japanese Patent Laid-Open No. 63-29039, each operating region having a throttle valve opening and an engine speed as parameters. The intake air amount corresponding to is stored, the opening degree and the rotation speed during operation are detected,
The stored intake air amount corresponding to each detected value is retrieved, and the intake air amount is set according to the retrieved intake air amount and the open or closed state of the opening / closing valve of the bypass passage bypassing the throttle valve. It is known to determine the fuel injection amount based on the fuel injection amount. As described above, by adding the intake air amount flowing through the bypass passage when determining the fuel injection amount, it is possible to determine the fuel injection amount by almost accurately grasping the air amount that has entered the surge tank.

[0003]

By the way, in the above, only the open or closed state of the on-off valve of the bypass passage is detected, and in the case of the open state, the intake air amount is also increased and corrected. The degree is not taken into consideration.

In recent years, a solenoid valve called a large-capacity ISC valve is provided in the bypass passage to control the idle speed (IS
There is known a configuration in which one solenoid valve is controlled to be opened / closed under various conditions in the case of C), and the engine speed during idling is maintained at a target speed. In such a configuration, the solenoid valve is controlled to be opened in accordance with the operating state of the engine at that time even when the engine is not idling. Therefore, for example, the opening varies depending on the load condition of the engine, and when estimating the intake air amount of the bypass passage provided with the solenoid valve, only the open and closed states as described above are required. Estimated by (1), there is no difference in the intake air amount due to the difference in the opening degree, and as a result, an accurate fuel injection amount may not be determined.

The object of the present invention is to eliminate such a problem.

[0006]

The present invention takes the following means in order to achieve such an object. That is, the air-fuel ratio control method for an internal combustion engine of the invention according to claim 1 of the present application is an internal combustion engine comprising an air flow control valve for controlling an intake air amount during idling in a bypass passage bypassing a throttle valve. An air-fuel ratio control method for an internal combustion engine, which calculates a fuel injection amount based on a valve opening degree and a rotation speed of the internal combustion engine,
The basic injection amount is determined based on the opening of the throttle valve and the rotation speed of the internal combustion engine, the opening of the air flow control valve is detected, and the detected opening of the air flow control valve and the rotation speed of the internal combustion engine The increase correction injection amount according to the bypass air flow rate of the bypass passage is determined based on the above, and the final fuel injection amount is determined from the basic injection amount and the increase correction injection amount.

The air-fuel ratio control method for an internal combustion engine according to a second aspect of the present invention is an internal combustion engine having an air flow control valve for controlling an intake air amount during idling in a bypass passage bypassing a throttle valve. In an air-fuel ratio control method for an internal combustion engine, which calculates a fuel injection amount based on an opening of a throttle valve and a rotation speed of the internal combustion engine, the opening of the air flow control valve is detected, and the detected air is detected. The present invention is characterized in that the opening degree of the throttle valve at that time is increased and corrected based on the opening degree of the flow control valve, and the fuel injection amount is determined based on the increased and corrected opening degree of the throttle valve and the rotation speed of the internal combustion engine. To do.

[0008]

As described above, according to the first aspect of the present invention, the final fuel injection amount depends on the bypass air flow rate of the bypass passage, the opening degree of the air flow rate control valve, and the rotation speed of the internal combustion engine. The increased correction injection amount determined based on the above is added. In this case, the increased correction injection amount is determined from the bypass air flow rate with the rotation speed of the internal combustion engine as a parameter, and therefore reflects the operating state of the internal combustion engine, and the final fuel injection amount is substantially the throttle valve. It accurately corresponds to the amount of air flowing into the downstream of. Therefore, it is possible to prevent the intake air amount from becoming excessive by the bypass air flow rate passing through the bypass passage and making the air-fuel ratio lean.

Further, according to the second aspect of the present invention, since the opening of the throttle valve is corrected based on the opening of the air flow control valve, the corrected opening of the throttle valve is the bypass passage. It reflects the flow rate of bypass air flowing into the. That is, the actual opening of the throttle valve and the corrected opening differ by an opening corresponding to the bypass air flow rate based on the opening of the air flow control valve at that time. Therefore, if the fuel injection amount is determined based on the corrected opening degree and the engine speed of the internal combustion engine, the fuel injection amount with respect to the intake air amount obtained by increasing the air amount corresponding to the bypass air flow rate can be determined. Becomes As a result, it is possible to prevent the intake air amount from becoming excessive by the bypass air flow rate that passes through the bypass passage and making the air-fuel ratio lean.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment (hereinafter referred to as a first embodiment) of the invention according to claim 1 of the present application will be described below with reference to the drawings.

The engine 100 schematically shown in FIG. 1 is for an automobile and its intake system 1 including a surge tank 12 is shown.
Is provided with a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown), and a bypass passage 3 that bypasses the throttle valve 2 is provided. The bypass passage 3 has an air flow control valve for idle speed control. The barrel flow control valve 4 is provided. The bypass passage 3 of the first embodiment has an auxiliary passage 31 that bypasses the flow control valve 4, and the auxiliary passage 31 is provided with an auxiliary flow control valve 32. The flow rate control valve 4 is an electronic opening / closing type, which is abbreviated as a large flow rate VSV, and its substantial opening is continuously controlled by controlling the operation duty ratio DISC of the drive voltage applied to its terminal 4a. The air flow rate of the bypass passage 3 can be adjusted. In other words, a set of the bypass passage 3 and the flow rate control valve 4 substantially unify the bypass passage that is normally provided for each correction item including the warm-up correction amount increase during idle operation. .
The auxiliary flow rate control valve 32 is different from the flow rate control valve 4, and is composed of, for example, a vacuum switching valve that opens when the control electrical signal is on and closes when the control electrical signal is off, and a relatively large load such as an air conditioner is applied. It is configured to open at the time. Then, the calculated duty ratio D
The ISC is determined by adding and subtracting the water temperature correction amount DAAV, which is the warming-up correction increase amount, the rotation feedback (F / B) correction amount DFB, and the like, including these.

The intake system 1 is further provided with a fuel injection valve 5, and the fuel injection valve 5 and the flow rate control valve 4 are controlled by an electronic control unit 6.

The electronic control unit 6 includes a central processing unit 7
And a storage device 8, an input interface 9, and an output interface 11 are mainly configured. The memory device 8 has a program for controlling the engine 100 and a main basic injection time with an engine speed NE and a throttle opening TA as parameters, which are data necessary for calculating the injector final energization time T. A first map formed of a two-dimensional map for determining TPTA, and a second map formed of a two-dimensional map for determining the auxiliary basic injection time TPISC using the engine speed NE and the calculated duty ratio DISC as parameters. Engine speed NE
At least a third map, which is a one-dimensional map for determining the load-time corrected injection time TPVSV, is stored as a parameter. Then, the input interface 9 has a rotation speed signal b output from a rotation speed sensor 14 for detecting the engine speed NE, a vehicle speed signal c output from a vehicle speed sensor 15 for detecting a vehicle speed, and a throttle valve 2 The opening degree signal d output from the throttle opening degree sensor 16 for detecting the opening degree TA of the engine, the water temperature signal e output from the water temperature sensor 17 for detecting the engine cooling water temperature as the engine temperature, etc. are input. It
Further, from the output interface 11, the fuel injection valve 5
On the other hand, a drive signal f corresponding to the calculated fuel injection time, a control signal g based on a calculated duty ratio DISC described later for the flow rate control valve 4, and a control signal g for the auxiliary flow rate control valve 32. The opening signals h are output respectively. Although not shown, the electronic control unit 6 includes an A / D for converting an input analog signal into digital data.
A converter is built in, and the cooling water temperature and the engine speed NE are converted into digital data at regular intervals and output to the central processing unit 7.

In the electronic control unit 6, the main basic injection time TPTA is determined by using the signals from the throttle opening sensor 16 and the rotation speed sensor 14 as main information, and various correction amounts are added to the main basic injection time TPTA. The basic injection time TP is determined in consideration of the above, the injector final energization time T is calculated from the effective injection time TAU calculated based on the main basic fuel injection amount TP, and the fuel injection is performed using the calculated injector final energization time T. A program for controlling the valve 5 to inject the fuel according to the load from the fuel injection valve 5 into the intake system 1 is incorporated. Prior to the calculation of the injector final energization time T, the main basic injection time TPTA, which is the basic injection amount, is determined based on the opening TA of the throttle valve 2 and the engine speed NE, and the air flow control valve is opened. Of the air flow rate control valve and the detected engine speed NE, the correction injection amount corresponding to the bypass air flow rate of the bypass passage 3 is determined. A program programmed to determine the final fuel injection amount is also included.

The schematic structure of this air-fuel ratio control program is
As shown in FIG. The basic injection time TP is calculated by the following equation.

TP = TPTA (NE, TA) + TPISC (NE, DISC) * KTPISC (TPTA) + TPVSV (NE) * KTPVSV (TPTA) (1) where TPISC; engine speed NE and opening of the flow control valve 3 Auxiliary basic injection time determined by (calculation duty ratio DISC is applicable), TPVSV; Loaded correction injection time determined by open / close (ON / OFF) of auxiliary flow control valve 32 and engine speed NE, KTP
ISC: main load correction coefficient based on main basic injection time TPTA, KTPVSV: secondary load correction coefficient based on main basic injection time TPTA.

In the first embodiment, the sum of the second term and the third term of the equation (1) is the corrected injection amount.

First, in step S1, the main basic injection time TPTA is determined by interpolating four points on the first map from the engine speed NE and the throttle opening TA. That is, the engine rotational speed NE is detected, it is determined which rotational speed region the detected engine rotational speed NE belongs to at two points on the first map, and the throttle opening TA is detected. The detected throttle opening TA is the first
It is determined to which opening area set by two points on the map, and the value set in the area defined by both the rotational speed area and the opening area is used as the main basic injection time TPT for this time.
Adopted as A. Thereafter, in step S2, similarly, four-point interpolation is performed on the second map from the engine speed NE and the calculated duty ratio DISC to determine the auxiliary basic injection time TPISC. The 4-point interpolation method in this step is also the same as that in step S1.

When the main basic injection time TPTA and the auxiliary basic injection time TPISC are determined in this way, the state of the load at that time is determined from the value of the main basic injection time TPTA in step S3, and the determined load magnitude is determined. The main load correction coefficient KTPISC that is increased or decreased according to Further, in order to determine the air flow rate of the auxiliary passage 31, in step S4, the load correction injection amount TPVSV is determined by interpolating the third map from the engine speed NE at this time. Further, similarly to step S3, in step S5, the slave load correction coefficient KTPVSV is calculated according to the magnitude of the load determined from the main basic injection time TPTA.

Next, at step S6, the basic injection time TP
The main basic injection time TPTA is temporarily stored as, and the value obtained by multiplying the basic injection time TP by the auxiliary basic injection time TPISC by the main load correction coefficient KTPISC is added and stored as a new basic injection time in step S7. . In this way, the auxiliary basic injection time TPI corrected by the main basic injection time TPTA and the main load correction coefficient KTPISC
Throttle valve 2 and flow control valve 4 depending on the sum of SC
The amount of air taken into the surge tank 12 is determined via the auxiliary flow rate control valve 32, and whether or not there is any amount of air taken in via the remaining auxiliary flow rate control valve 32 is determined in step S8. Whether it is open or not is determined. If it is open, the process proceeds to step S9, and if it is closed, this routine is finished as it is. Auxiliary flow control valve 32
Is opened, in step S9, the basic injection time TP stored at this time is multiplied by the load correction coefficient KTPVSV according to the load correction injection time TPVSV, and the result is added. The final basic injection time TP is calculated.

That is, when there is no large load such as the air conditioner, the control proceeds to steps S1 to S7 and step S1.
After executing 8, proceed to another routine. In this case, the basic injection time TP depends on the engine speed NE and the throttle opening T.
It is determined based on the main basic injection time TPTA determined by A and the auxiliary basic injection time TPISC determined by the engine speed NE and the calculated duty ratio DISC which is the opening of the flow control valve 4 in the bypass passage 3. To be done. On the contrary, when the air conditioner is used, the auxiliary flow control valve 32 is opened because it is necessary to idle up accordingly, so the control advances to steps S1 to S9. In this case, by executing steps S7 and S9, the basic injection time TP is calculated by the above equation (1).

As described above, the auxiliary basic injection time TPISC determined based on the engine speed NE and the opening degree (calculated duty ratio DISC) of the flow control valve 4 and the engine speed NE when the engine is open are used. The corrected injection time TPVSV under load determined by the main basic injection time TPTA
The main correction injection time TPTA is corrected on the basis of the load state at that time obtained from
Since the correction is made in step 1, the intake air amount of the bypass passage 3 can be calculated in a state in which the operating state of the engine 100 is reflected, and the air-fuel ratio can be prevented from becoming lean.

FIG. 3 is a flow chart showing a schematic configuration of an air-fuel ratio control program in an embodiment (hereinafter, referred to as a second embodiment) of the invention according to claim 2 of the present application. The engine to which the second embodiment is applied does not include the auxiliary passage 31 unlike the engine of the first embodiment shown in FIG. Therefore, only the bypass passage 3 bypasses the throttle valve 2. Further, the electronic control unit may be the same as the first embodiment except for the programs and data stored in the storage device. In the second embodiment, the current throttle opening is increased and corrected by the corrected throttle opening ΔTA according to the cross-sectional area of the bypass passage 3 which is determined by the opening of the flow rate control valve 4 provided in the bypass passage 3. , The amount of fuel injection is determined.

In FIG. 3, in step S21, the detected throttle opening TA and engine speed NE at the present time are read. In step S22, the bypass passage 3
It is determined whether or not the amount of bypass air that passes through the throttle valve 2 and flows into the downstream side of the throttle valve 2 is zero.
5, the process proceeds to step S23 if not.
This determination is to determine 0 when the numerical value of the calculated duty ratio DISC that is the actual opening of the flow control valve 4 is 0 (%). In step S23, step S22
The corrected throttle opening .DELTA.TA is determined from the value of the calculated duty ratio DISC determined in. Corrected throttle opening ΔT
As shown in FIG. 4, A is set to increase as the substantial area of the bypass passage 3 increases, and is representative of the calculated duty ratio DISC of the flow control valve as a value indicating the area. Corresponding values are set in the two-dimensional map, and values not in the two-dimensional map are determined by performing interpolation calculation. In step S24, the throttle opening TA at this time and the corrected throttle opening ΔTA determined in step S23 are added to calculate the throttle opening TA used for calculating the fuel injection amount. Step S
In 25, the two-dimensional map is searched based on the obtained throttle opening TA and engine speed NE, and the fuel injection amount is calculated and determined.

In such a structure, the bypass passage 3
When the engine is closed, there is no air flowing through the bypass passage 3, so the control proceeds to steps S21 → S22 → S25, and the fuel is based on the read current throttle opening TA and engine speed NE. The injection amount is determined.

On the other hand, for example, when the load is applied to the engine and the flow control valve 4 is opened, the control is performed in step S2.
1 → S22 → S23 → S24 → S25, and the opening degree of the flow rate control valve 4 at that time, that is, the calculated duty ratio D
The corrected throttle opening ΔTA is determined according to the ISC, and the fuel injection amount is calculated with the throttle opening TA corrected according to the bypass air amount passing through the bypass passage 3.

As described above, the throttle opening TA is increased and corrected according to the cross-sectional area of the bypass passage 3, so that the intake air amount (bypass air amount) sucked through the bypass passage 3 passes through the throttle valve 2. It will be added to the intake air amount. In this case, the calculation of the fuel injection amount is
Since the throttle opening TA actually used for the calculation is corrected in advance according to the opening of the flow control valve 4, the calculation itself is the same as when the flow control valve 4 is closed. That is, also in this calculation, the same engine speed NE and throttle opening T as when the flow control valve 4 is closed are used.
The calculation is performed using the two-dimensional map set by A and A. Therefore, it is not necessary to set a plurality of two-dimensional maps to be referred to when calculating the fuel injection amount according to the state of the flow control valve 4, and the data structure can be simplified. Further, since the amount of fuel injected increases by the correction throttle opening amount ΔTA, even if the amount of intake air passing through the bypass passage 3 increases, the fuel injection amount is constantly increased in accordance with the amount of air, and the air-fuel ratio is increased. Never becomes lean. As a result, it is possible to prevent the drivability from deteriorating and suppress the deterioration of the emission.

The present invention is not limited to the embodiment described above. For example, in the first embodiment,
The bypass passage 3 does not need to have the auxiliary passage 31, and the flow control valve 4 can be applied to various loads including the air conditioner.
May be configured to respond by controlling the opening degree. That is, when calculating the calculation duty ratio DISC, a program is executed to correct the basic amount according to the load of the air conditioner, headlight, defogger, etc., and adjust the opening of the flow control valve 4 according to the load. In addition to the above, when calculating the basic injection amount TP, {TPV of the equation (1) in the first embodiment is used.
The configuration may be such that the SV (NE) * KTPVSV (TPTA)} term is deleted. Therefore, in the program, steps S4, 5 and S of the flowchart shown in FIG. 2, which is the program in the first embodiment, are executed.
It is sufficient to delete 8 and 9. It should be noted that, in such another embodiment, the main basic injection time TPTA and the auxiliary basic injection time TP
As a matter of course, the ISC and the like are set to values different from those in the first embodiment.

On the contrary, in the second embodiment, the bypass passage 3 may be provided with the auxiliary passage 31 having the auxiliary flow rate control valve 32, as in the first embodiment. In this case, the auxiliary flow rate control valve 32 is fully open and fully closed.
Since there are only two states, the auxiliary correction throttle opening Δ
Different from the corrected throttle opening ΔTA, TAs may be set to a constant value. When it is detected that the auxiliary flow rate control valve 32 is open, the auxiliary correction throttle opening ΔT is determined in step S24 in the second embodiment.
As is the throttle opening TA and the corrected throttle opening ΔTA
And may be added to and calibrated to calculate the corrected throttle opening TA.

In the first embodiment, the main load correction coefficient KTPISC is calculated according to the size of the fuel cut judged from the main basic injection time TPTA. Alternatively, it may be determined based on a two-dimensional map using as a parameter. Thus, the main load correction coefficient KTPISC
By adding the calculated duty ratio DISC to the determination of, the load state can be more accurately determined by the main load correction coefficient KTPISC.
Can be reflected in.

In addition, the configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the gist of the present invention.

[0032]

As described in detail above, the present invention determines the fuel injection amount in a state where the intake air amount passing through the bypass passage bypassing the throttle valve is added to the intake air amount passing through the throttle valve. Therefore, the air-fuel ratio can be prevented from becoming lean, and good drivability can be reliably exhibited. Moreover, since the air-fuel ratio is not biased to the lean side, it is possible to reliably suppress the deterioration of emission. Moreover, in the invention according to claim 2, since the opening degree of the throttle valve at that time is increased and corrected based on the opening degree of the air flow control valve in the bypass passage,
When calculating the fuel injection amount based on the opening degree of the throttle valve and the engine speed of the internal combustion engine, the same calculation method is used to determine the fuel injection amount regardless of the degree of opening of the air flow control valve. be able to.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing an embodiment of the invention according to claim 1 of the present application.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is a flowchart showing a control procedure of an embodiment of the invention according to claim 2 of the present application.

FIG. 4 is an operation explanatory view of the embodiment of the invention according to claim 2 of the present application.

[Explanation of symbols]

 2 ... Throttle valve 3 ... Bypass passage 4 ... Flow control valve 6 ... Electronic control device 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 11 ... Output interface

Claims (2)

[Claims] 1. An internal combustion engine having an air flow control valve for controlling an intake air amount during idling in a bypass passage bypassing a throttle valve, based on an opening of the throttle valve and a rotational speed of the internal combustion engine. An air-fuel ratio control method for an internal combustion engine, which calculates a fuel injection amount, wherein a basic injection amount is determined based on an opening degree of a throttle valve and an internal combustion engine, and an opening degree of the air flow control valve is detected. Based on the detected opening of the air flow control valve and the number of revolutions of the internal combustion engine, an increase correction injection amount is determined according to the bypass air flow rate of the bypass passage, and the final correction amount is determined from the basic injection amount and the increase correction injection amount. A method for controlling an air-fuel ratio of an internal combustion engine, characterized by determining a proper fuel injection amount. 2. An internal combustion engine comprising an air flow control valve for controlling an intake air amount during idling in a bypass passage bypassing a throttle valve, based on an opening of the throttle valve and a rotation speed of the internal combustion engine. An air-fuel ratio control method for an internal combustion engine, which calculates a fuel injection amount, wherein the opening of the air flow control valve is detected, and the opening of the throttle valve at that time is determined based on the detected opening of the air flow control valve. An air-fuel ratio control method for an internal combustion engine, wherein the fuel injection amount is determined on the basis of the opening correction of the throttle valve and the rotation speed of the internal combustion engine that have been corrected for increase.