JPH01294931A - Air-fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To enable high-precise control of an air-fuel ratio despite of the change in opening of an intake air control valve, by a method wherein a value by which a lag in the control state of an air-fuel ratio is reflected is stored according to the opening of an intake air control valve on the downstream of a throttle valve, and by referring to the memory value, a feed fuel amount is controlled. CONSTITUTION:In an engine MD having an intake air control valve MC located on the downstream of a throttle valve MA, an air-fuel ratio correction value is fixed by an air-fuel ratio control means MH based on an output from a running state detecting means ME, and based on the detecting result of the air-fuel ratio detecting means ME, regulation of the air-fuel ratio correction value is made. During regulation of the air-fuel ratio correction value, a learning value is calculated by a learning means MI based on a difference between the air-fuel ratio correction value and a reference value, and is stored according to an output from an opening detecting means MF to detect the opening of the intake air control valve MC. A fuel feed means MJ calculates a fuel feed amount based on a running state, and corrects the fuel feed amount by means of the air-fuel correction value and the memory value of the learning means MI.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an air-fuel ratio control device for an engine, which is provided with an intake control valve between a throttle valve and a combustion chamber that controls intake air independently of the throttle valve. Regarding.

[Conventional technology] Conventionally, in order to stably operate an engine at a lean air-fuel ratio,
Alternatively, in order to improve engine output, fuel efficiency, emissions, etc., there is a technology that installs an intake control valve near the combustion chamber to control intake air, or detects the air-fuel ratio of the exhaust gas and adjusts the engine air-fuel ratio to a predetermined air-fuel ratio. Technology has been developed to control this.

By performing high-precision control, such technology
This makes it possible to maintain the operating state of the engine at a predetermined lean air-fuel ratio or to operate the engine appropriately. Therefore, in order to make this possible, the following air-fuel ratio control technology has been disclosed. ■Technology related to intake control valve: The intake control valve, which operates independently of the throttle valve, has a This has various effects on the operating state of the engine, especially the intake pipe pressure, and causes an error in the basic fuel injection amount calculated from the intake pipe pressure. Therefore, in order to prevent errors in the fuel injection amount due to the opening degree of the intake control valve, the fuel injection amount required by the engine is calculated for each intake control valve opening degree (Japanese Patent Laid-Open No. 59-200028). Publication No.).

■Technology to maintain the engine's air-fuel ratio at a lean air-fuel ratio:
Since it is not possible to accurately control the air-fuel ratio with conventional lean control using open control, air-fuel ratio feedback control is performed using the output of a lean mixture sensor whose output changes depending on the oxygen moisture content (Japanese Patent Application Laid-Open No. 1983-1999). 329
Publication No. 46).

■Technology for transitioning from lean feedback control to open control according to (■) above: Since lean feedback control can only be performed when specific feedback conditions are met, control when transitioning to open control is also required. Here, simply shifting to open control will not allow subsequent lean control to be performed accurately.

Therefore, the operating state during feedback is learned, and during oven control faj, fuel injection is performed based on this learned value, and the response delay peculiar to this learning control is corrected by tilting the air-fuel ratio to the rich side ( Unexamined Japanese Patent Publication 1986-206
Publication No. 953).

[Problems to be Solved by the Invention] However, in the conventional technology, when the opening of the intake control valve changes or when air-fuel ratio feedback control shifts to air-fuel ratio oven control, the engine There is a problem in that the air-fuel ratio deviates from a predetermined air-fuel ratio, leading to deterioration in drivability or emissions.

■Calculate the fuel supply amount based on the intake pipe pressure PM and engine speed NE, calculate the intake temperature correction coefficient FTHA from the intake air temperature TI (A, and use the map shown in Figure 9 to correct the intake air temperature of the fuel injection amount. In this case, the intake temperature correction coefficient FTHA is made smaller as the intake air temperature increases, and the fuel supply amount is corrected to decrease.In this case, the intake air temperature sensor is installed relatively upstream of the intake air passage, for example, near the air cleaner. The intake air is thermally influenced by the intake passage before it is actually taken into the combustion chamber, and the temperature THA of the air actually taken into the combustion chamber is the measured value THA by the intake air temperature sensor. (There is a discrepancy with iM.

Moreover, the thermal effect also changes depending on the flow rate and flow velocity of the intake air, so by blocking more than half of the opening area of the intake control valve near the combustion chamber, for example, the intake boat, it is possible to If a swirl control valve SCv for forming a swirl is provided,
As shown in Figure 10, the swirl control valve S
By opening and closing the CV, the measured value THA and the actual intake temperature T
The deviation from HiM becomes larger as the temperature becomes lower. Therefore, when the swirl control valve SC■ is provided, the intake temperature correction coefficient FTH increases as the temperature decreases.
There is a problem in that the error in A increases and the accuracy of air-fuel ratio control decreases.

■The above problem ■ is automatically corrected while air-fuel ratio feedback control is being performed, but when air-fuel ratio feedback control shifts to air-fuel ratio open control, it becomes an error in the air-fuel ratio control section. , resulting in a decline in drivability, fuel efficiency, and emissions. In other words, in the conventional technology, the fuel supply amount calculated from the engine operating state is corrected by feedback control, and the error in the fuel supply amount calculated based on this correction state is learned. The fuel supply amount is controlled based on the learned value. However, the engine operating state, which is the basis for learning during feedback, varies greatly depending on the open/closed status of the swirl control valve SCV, so the learned value, which is the basis for open control, does not accurately reflect control errors. I couldn't say that. In addition, the intake temperature correction coefficient FTHA can be calculated according to the opening degree of the swirl control valve SCV, but since the relationship between the measured value THA and the actual intake temperature THiM varies depending on the intake air amount. There was a problem in that the accuracy of fuel ratio control could not be prevented from decreasing.

An object of the present invention is to improve the accuracy of air-fuel ratio control of an engine by solving the above problems.

[Means for Solving the Problems] As a means for solving the above objects, an air-fuel ratio control device for an engine according to the present invention, as illustrated in FIG. An engine MD comprising an intake control valve MC provided downstream of the throttle valve MA and near a combustion chamber MB, the engine MD comprising an operating state detection means ME for detecting the operating state of the engine MD. and the above-mentioned intake air amount (opening degree detection means M for detecting the opening degree of the wholesale valve MC)
P, an air-fuel ratio detection means MG for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine MD, and fixing an air-fuel ratio correction value for controlling the air-fuel ratio to a reference value based on the operating condition, if is an air-fuel ratio detecting means MH that increases or decreases based on the detection result of the air-fuel ratio detecting means MG.
When the air-fuel ratio control means MH increases or decreases the air-fuel ratio correction value, a learned value is calculated based on the difference between the air-fuel ratio correction value and the reference value, and the opening degree of the intake control fall valve MC is calculated based on the difference between the air-fuel ratio correction value and the reference value. and a learning means MI that stores/memorizes correspondingly, and calculates a fuel supply amount based on the above-mentioned operating state, and corrects the fuel supply amount by the above-mentioned air-fuel ratio correction 1st shift and the stored value of the learning means Ml. , a fuel supply means MJ that supplies fuel to the engine MD.

[Function] Provided downstream of the throttle valve MA of the present invention, the combustion chamber M
The air-fuel ratio control device for the engine MD, which includes the intake control valve MC disposed near B, first detects the operating state detection means ME.
Based on the detected operating state and the air-fuel ratio detected by the air-fuel ratio detection means MG, the air-fuel ratio control means MH sets the air-fuel ratio correction value as a reference so that the air-fuel ratio of the engine MD becomes a predetermined air-fuel ratio. Fixed to a value or increased or decreased. Then,
When the air-fuel ratio control means (M) (decreases the air-fuel ratio correction value by 1!), the learning means MI calculates a learned value based on the difference between the air-fuel ratio correction value and the reference value, and The opening detection means MP stores the detected opening of the intake control valve MC.Next, the fuel supply means MJ stores the opening of the intake control valve MC detected by the opening detection means MP.Next, the fuel supply means MJ stores the opening of the intake control valve MC based on the above-mentioned states, that is, the operating state, the air-fuel ratio correction value, and the learning means. M.I.
Based on the stored value, the fuel supply amount is calculated, the air-fuel ratio is corrected, and the fuel is supplied to the engine MD. As a result, the memory content of the learning means MI reflects the control error mainly caused by the change in the opening degree of the intake control valve MC, and the air-fuel ratio of the engine MO is determined based on the memory content of the learning means Ml. Also during fuel ratio feedback control and air-fuel ratio open control,
The control fail error is corrected, and the air-fuel ratio is controlled to a predetermined air-fuel ratio with high precision.

[Example] An example of the present invention will be described in detail below based on the drawings.

FIG. 2 is a schematic diagram of an air-fuel ratio control device for an engine as an embodiment of the present invention.

As shown in the figure, the intake pipe 4 of the engine 2 includes, from upstream,
Air cleaner 6, throttle valve 10° surge tank 12. Swirl control valve (abbreviated as SCV) 1
5 is provided. The air cleaner 6 is provided with an intake temperature sensor 1B that detects the temperature of intake air. The amount of air that passes through the intake pipe 4 and is taken into the combustion chamber 20 of the engine 2 is adjusted by controlling the opening and closing of the throttle valve 10. A throttle opening sensor 22 is attached to the throttle valve 10 to detect this opening.

A surge tank 12 provided further downstream of the intake vIl
is for suppressing intake pulsation, and the intake pressure sensor 2 detects the absolute pressure in this tank (intake pipe pressure PM).
It is equipped with 6. In addition, the intake system is also provided with an idle speed control valve 2 which controls the amount of idle air that bypasses the throttle valve 10, a fuel injection valve 29 which injects fuel into the intake air to form an air-fuel mixture, and the like. ing.

The swirl control valve (SCV) 15 driven by the swirl drive device 30 has two valves formed by partitioning the intake boat 31 with a partition plate 32, as shown in FIG. It is provided on one side of the passages 33 and 34, and the passage 33
It opens and closes. Swirl control valve 1
The rotating shaft 37 of No. 5 is connected to a drive shaft 41 of a pneumatic actuator 40, and is controlled by the operation of a negative pressure switching valve 45 connected to a pressure chamber 42 of this actuator 40 via a negative pressure transmission valve 43. , open◆valve is closed. That is, by using the negative pressure in the intake pipe 4 held by the negative pressure holding check valve 47 and opening the negative pressure switching valve 45, the actuator 40 is actuated, and the drive shaft 41 is moved in the direction of the arrow in FIG. direction, the swirl control valve 15
It closes. Here, the negative pressure transmission valve 43 includes a poppet valve and functions as a one-way valve, so the swirl control valve 15 opens slowly and closes instantly.

In addition, the engine 2 includes a distributor 52 that distributes the high voltage output from the igniter 50 to the combustion chambers 200 and spark plugs (not shown) as the engine 2 rotates, and a distributor 52 that distributes the high voltage output from the igniter 50 to each combustion chamber 200 and spark plugs (not shown). A lean mixture sensor 54 for detecting the temperature, or a coolant temperature sensor 58 provided in the overjacket 56 of the engine 2 for detecting the temperature of the coolant are provided. Note that the distributor 52 is provided with a rotation speed sensor 60 that detects the rotation angle of the engine 2 and the like.

Such a lean mixture sensor 54. A group of sensors such as a cooling water temperature sensor 581 and a rotation speed sensor 60, and a fuel injection valve 29. A group of actuators such as the negative pressure switching valve 45 of the swirl drive device 30 is connected to an electronic control II device 70 that controls fuel injection of the engine 2. This electronic control device 70 includes a well-known CPU 71. ROM72. RAM74
．． A timer 75 and the like are configured as a so-called arithmetic and logic operation circuit, and a human power port door 8 connected to the sensor group and an output port door 9 connected to the actuator group are interconnected with the CPU 71 and the like via a bus 77. It is configured as follows.

Opening and closing of the swirl control valve 15 is a well-known technique that is performed based on the intake pipe pressure PM and the engine speed NE, so the details are not shown in the figure, but in the electronic control device 70, an SCV control routine (not shown) is performed.
Referring to the map shown in FIG. 5, the opening/closing of the SCV is determined at B and 6 L, and control is performed by outputting an SCV drive signal based on this result. For example, when the engine 2 is under extreme load, that is, the engine speed NE is less than the rotation speed N1, and the intake pipe pressure PM
is less than P1, the swirl control valve 15
is brought into a closed state (SCV closed).

Next, a flowchart of a fuel injection amount calculation routine that is repeatedly executed in the electronic control unit 70 is shown in FIG. 4, and the control section of this embodiment will be explained based on this flowchart.

When this routine is started, it first refers to the flag of the Sc control routine described above and reads whether the swirl control valve 15 is closed (SCV closed) or open (between SCVs), and then Read the intake pipe pressure PM calculated from the output of the intake pressure sensor 26,
The learning value KG (=KGjS or KGio, i=1 to 7) corresponding to this read value and the flag XKG (=$01 to $CO) indicating it are read from the learning value map shown in FIG. Step 100).

For example, when the SCV is closed, the intake pipe pressure PM is 500 mmt.
In the case of 1g, the learning value K G 5 S and the flag $1
Read 0.

Next, it is determined whether the air-fuel ratio feedback (A/F, F/B) conditions by the lean mixture sensor 54 are satisfied. A judgment is made by determining whether all conditions such as not being cut are met (step 1, step 0).

Here, if the A/F and F/B conditions are satisfied, as shown in FIG. The center value FAFAV of the coefficients is calculated as shown below (step 130). Air fuel ratio correction II! IF A F is calculated by, for example, skipping the value of air-fuel ratio correction f+W F A F from A at the time TO when the air-fuel ratio determination by the lean mixture sensor 54 leans toward the richer side than a predetermined air-fuel ratio. F decreases until the next time point TI when the determination by the lean mixture sensor 54 reverses to the lean law.
This is done by repeating the process of decreasing AF by a predetermined value per unit time. In addition, air-fuel ratio correction (direct center value F
Calculation of AFAV is performed using, for example, the slope at the time of reversal of the air-fuel ratio correction value FAF (time To = A, time TI = B.

It is obtained by calculating the average value at time T2=C, time T3=D, . . . ). For example, at time T2, FAFAV=
It is calculated by performing the multiplication of (B+C)/2.

After determining the central 1st shift FAFAV of the air-fuel ratio correction value, it is then determined whether or not this FAFAV is not the value 1 (step 140), thereby determining whether it is necessary to update the learning (aKG). Here, if it is determined that it is necessary to update the learning 1 shift KG, then it is determined whether the center value FAFAV of the air-fuel ratio correction value is larger than the value 1 (Step 150), FAFAV If >1, the learning 11 mode (G) read in step 100 described above is
For example, add 0°002 (step 160), FAF
If AV is less than 1 Yoshi 1, a process of subtracting, for example, 0°002 from the learned value IG is performed to update the learned value M shown in FIG. 6 (step 170). As a result, the learned value KG increases or decreases so that the air-fuel ratio correction (direct FAF becomes the value 1).

After updating the learning value KG, the fuel injection amount TAU is calculated based on the following equation (1) (step 180).

TALJ= (KGiS or KGiO) *FA
F*FTHA*Tp * (KLEAN+α)+Tv...(1) FTHA
...Intake temperature correction coefficient (see Figure 9).

Tp...Basic fuel injection amount KLEAN...Lean correction coefficient α...Other correction coefficients Tv...Invalid injection time The basic fuel injection amount Tp is based on intake pipe pressure PM, engine speed NE, and SCV. This is a value calculated according to the map shown in FIG. 8 based on whether the door is opened or closed.

The lean correction coefficient KLEAN is used to adjust the air-fuel ratio of the engine 2 to a predetermined lean air-fuel ratio,
Based on engine speed NE and intake pipe pressure PM,
This value is calculated from the optimum air-fuel ratio A/D calculated according to the map shown in FIG. 5, taking into consideration the characteristics of the lean mixture sensor 54, etc. For example, as shown below, this lean correction coefficient KLEAN is
This air-fuel ratio is used as the basis for determining whether the target lean air-fuel ratio is rich or lean.

(2) The output current of the lean mixture sensor 54 has a value corresponding to the oxygen partial pressure in the rotary air, and the output increases almost linearly as the air-fuel ratio increases. Therefore, from the above relationship, a map showing the relationship between the air-fuel ratio of the engine 2 and the output value of the lean mixture sensor 54 is calculated.

(2) The lean correction coefficient KLEAN is set corresponding to the map (2).

(2) Therefore, by comparing the slope IR of K L E A N and the output 1i L N S R of the lean mixture sensor 54, it is possible to judge whether the mixture is rich or lean. For example, IR≧LNSR→rich, ■R<LN
It is determined that SR→Lean.

According to this routine above, the fuel injection amount jAU is calculated,
It becomes possible to refer to it in a fuel injection execution routine (not shown).

When the lean mixture sensor 54 determines whether the air-fuel ratio feedback (A/F, F/B) conditions are satisfied, if it is determined that the A/F and F/B conditions are not satisfied, ( Step 110), then set the air-fuel ratio correction coefficient FAF to 1 shift 1 (step 190), and calculate the combustion injection amount TA U as described above (step 180).
, the engine 2 is controlled by an air-fuel ratio oven control section. Therefore, in this case, the fuel injection amount TAU of the engine 2 is determined based on the learned value KG without updating the learned value KG.
Control the oven with high precision.

By determining whether the central value FAFAV of the air-fuel ratio correction value is not 1 (step 140), if it is determined that there is no need to update the learning value KG, the learning (direct KG) is determined. Without updating, the fuel injection amount T
Calculate AU (Step 180).

As described above, in this embodiment, the opening/closing state of the swirl control valve 15 and the cargo (intake pipe pressure PM) of the engine 2 are explained.
Based on this, the engine's air-fuel ratio control state is learned and used as a reference when calculating the fuel injection amount.

As a result, as shown below, the accuracy of air-fuel ratio control is improved when the open/closed state of the swirl control valve 15 changes, and when the air-fuel ratio feed pump control is shifted to air-fuel ratio oven control, and the drivability is improved. It has the extremely excellent effect of improving fuel efficiency and emissions.

(2) Errors in intake air temperature greatly affect the order of calculation when calculating the fuel injection amount TAU. However, in this embodiment, since a learning value that reflects this error is obtained for each opening/closing state of the swirl control valve 15, which is the cause of the error in intake air temperature, the opening/closing of the swirl control valve 15 occurs when the air-fuel ratio is fed back. In either case, or during oven control of the air-fuel ratio, the calculated value of the fuel injection amount can be determined with high accuracy based on this learned value. As a result, the air-fuel ratio control of the engine 2 is executed with high accuracy using the learned value that reflects the actual intake air temperature, not only during air-fuel ratio feedback but also during air-fuel ratio oven control.

■ Even when the air-fuel ratio feedback control is shifted to the air-fuel ratio oven control section, as shown in ■ above, the learned value is stored for each of the various operating conditions and error occurrence factors of the engine 2. Because of this, engine 2
The air-fuel ratio can be accurately controlled to a desired value.

Note that the present invention is not limited to the above embodiments,
Various embodiments can be implemented without departing from the gist of the present invention. For example, instead of the swirl control valve, any valve that similarly controls intake air may be used, or instead of the lean mixture sensor 54, an 02 sensor may be used to perform air-fuel ratio feedback control. There may be.

[Effects of the Invention] The air-fuel ratio control device for an engine according to the present invention adjusts a value that reflects a deviation in the control state of the air-fuel ratio of the engine to a value that corresponds to the opening degree of the intake control valve provided near the combustion chamber of the engine. This stored value is used to control the amount of fuel supplied to the engine. Therefore, no matter how the opening degree of the intake control valve changes, it reflects the error in air-fuel ratio control at this time (l
σ can be stored and reflected during control. As a result, even if the opening of the intake control valve changes, air-fuel ratio feedback control and air-fuel ratio oven control can be performed with high precision, making it possible to improve drivability, fuel efficiency, and emissions. It has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the basic configuration of an engine air-fuel ratio control device of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is a partial block diagram thereof, and FIG. The flowchart of the fuel injection amount calculation routine, FIG. 5 is an explanatory diagram of the SCV opening/closing map, FIG. 6 is an explanatory diagram of the learned value map, FIG. 7 is an explanatory diagram of the operation of the embodiment, and FIG. 8 is an explanatory diagram of the SCV opening/closing map. FIG. 9 is a graph showing the characteristics of the intake temperature correction coefficient, and FIG. 10 is an explanatory diagram of a conventional example. MA...Front valve, MB...Combustion chamber, MC...
...Intake control valve, MD...Engine, ME...Operating state detection means, MP...Opening degree detection means, MG...Air-fuel ratio detection means, MH...Air-fuel ratio control means, XI...・・・
learning means, MJ... fuel supply means, 2... engine, 10... throttle valve, 15... swirl control valve, 2G... intake pressure sensor, 54...
...Lean mixer sensor, 70...Electronic control device agent Tsutomu Sadatetsu, patent attorney (and 2 others) Figure 1 Figure 3 Figure 6 Figure 7 1 l l Figure 8 Engine speed NErrprr1ノ

Claims (1)

[Scope of Claims] An engine comprising a throttle valve for controlling the amount of intake air, and an intake control valve provided downstream of the throttle valve and near a combustion chamber, wherein the engine is configured to control the operating state of the engine. an operating state detection means for detecting the opening of the intake control valve; an opening detection means for detecting the opening of the intake control valve; an air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; air-fuel ratio control means that fixes the fuel ratio correction value to a reference value based on the operating state or increases or decreases it based on the detection result of the air-fuel ratio detection means; and the air-fuel ratio control means increases or decreases the air-fuel ratio correction value. When you are there,
learning means for calculating a learning value based on the difference between the air-fuel ratio correction value and the reference value and storing the learning value in correspondence with the opening degree of the intake control valve; An air-fuel ratio control device for an engine, comprising: a fuel supply unit that corrects the fuel supply amount using the air-fuel ratio correction value and a stored value of a learning unit, and supplies fuel to the engine.