JP2001234798A - Air-fuel ratio control device of internal combustion engine and method for estimating intake air quantity of each of cylinders - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely find intake air quantity of each of cylinders even when a driving state of an internal combustion engine is variously changed without forming a map of intake air efficiency for each of the cylinders for each of engines. SOLUTION: An air-fuel ratio is controlled by measuring density of gas in a manifold, measuring quantity of air passing through a throttle, measuring an angle of a crank of the internal combustion engine, discriminating a cylinder in an air intake stroke in accordance with the crank angle, calling a computing means to correspond to the cylinder in the air intake stroke, assuming air intake efficiency by the computing means, computing the air quantity flowing into the cylinder in accordance with the air intake efficiency and the above sensor data and calculating fuel injection quantity to the cylinder in accordance with the air quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an air-fuel ratio control technique for controlling the ratio of the amount of air taken into a cylinder to the amount of fuel injected into the cylinder in order to improve the fuel efficiency of an internal combustion engine and reduce harmful substances in exhaust gas. About. In particular, the present invention relates to a technique for eliminating variations in air-fuel ratio for each cylinder.

[0002]

2. Description of the Related Art In order to control the air-fuel ratio of an internal combustion engine, the amount of air taken into a cylinder is measured and the fuel injection amount is calculated and controlled based on the measured amount, or the air-fuel ratio is measured from exhaust gas. There is a method of controlling the fuel injection amount so as to keep this at a target value. Until now, as a device for measuring the amount of air taken into the cylinder of an internal combustion engine or a device for measuring the air-fuel ratio, Japanese Patent Application Laid-Open No. 7-42600 No. 1 using a pressure sensor attached to a manifold, a device using a hot-wire type air flow meter mounted on an intake system pipe such as that disclosed in JP-A-9-166464, and a device disclosed in JP-A-7-133738. In some cases, an air-fuel ratio sensor is attached to the exhaust system piping to provide feedback so as to maintain the air-fuel ratio of exhaust gas at a target value.

In general, the amount of air Mc taken into a cylinder is
It is widely known that the pressure is proportional to the manifold pressure Pm and the number of revolutions N of the crank, and can be approximated by Mc = Pm ^* N ^* η ^* Vc / R ^* Tm. Here, it is the volume Vc of the cylinder, the gas constant R, and the temperature Tm of the gas in the manifold. η is called intake efficiency (sometimes referred to as charging efficiency, volume efficiency, etc., depending on the literature), and the loss of inflow into the cylinder depends on the shape of the manifold / cylinder inlet and the timing of opening / closing of the intake valve at the cylinder inlet. Is the value of what percentage of air is taken into the cylinder as a result of the loss. Since η varies slightly depending on the manifold pressure Pm and the crank rotation speed N, η is represented as a map of Pm and N.

Japanese Patent Application Laid-Open No. 7-42600 employs a so-called speed density method. In this method, a map of intake efficiency as a function of engine speed and intake manifold pressure is prepared in advance, and during operation, engine speed and manifold pressure are measured, and engine speed and manifold pressure are measured. The intake air amount was calculated based on the intake efficiency obtained by searching the map from, the observed engine speed, and the intake manifold pressure. In this system, the intake air efficiency that changes depending on the operating state of the internal combustion engine is searched from a map, so that the correct amount of intake air to the cylinder can be calculated even when the operating state changes.

In Japanese Patent Application Laid-Open No. 9-166644, the amount of air flowing into a cylinder is measured by a hot-wire type air flow meter. In this method, a hot-wire air flow meter is arranged in an intake inflow passage upstream of a cylinder, and the amount of air that passes through a cross section provided with the hot-wire air flow meter is measured. In this method, since the absolute amount of the passing air is directly obtained, there is an advantage that a map of the intake efficiency is not required.

In Japanese Patent Application Laid-Open No. Hei 7-1333738, an air-fuel ratio is measured, not an air amount, and the fuel injection amount is controlled so as to maintain the air-fuel ratio at a target value. In this method, one wide-area air-fuel ratio sensor is arranged in the exhaust system collecting part, and the rotation of the exhaust cylinder and the delay from exhaustion from the cylinder to influence on the air-fuel ratio sensor are modeled, and the air-fuel ratio for each cylinder is modeled. Is to be estimated by the observer. In this method, the air-fuel ratio for each cylinder, which has not been considered in the above-mentioned two known examples, is measured.

Further, regarding the intake air amount, Japanese Patent Laid-Open No. 9-228
Nos. 84, 9-126006, and 11-6460 are mentioned.

[0008]

It is said that the amount of air entering a cylinder of an internal combustion engine varies from about 5% to about 10% for each cylinder. For this reason, if the same amount of fuel is injected into all cylinders, the air-fuel ratio differs for each cylinder, and harmful substances such as hydrocarbons in the exhaust gas will be emitted in the cylinders in which the fuel is injected more than the target air-fuel ratio. In a cylinder in which fuel is injected less than the target air-fuel ratio, there is a problem that the ratio of nitric oxide increases and torque becomes uneven.

[0009] An average of the intake efficiencies when air flows from the manifold to all the cylinders is held as an intake efficiency map. If the manifold pressure is constant, the same amount of fuel is injected into all the cylinders. In this case, variations occur in the air-fuel ratio for each cylinder.

In a method in which the amount of air flowing into the intake manifold is accurately determined, but the ratio of the air flowing into the manifold to be distributed to each cylinder is not considered, the air is distributed to all the cylinders at the same ratio. Therefore, the air-fuel ratio varies from cylinder to cylinder.

[0011] The air-fuel ratio of the air that reaches the exhaust pipe through the combustion and exhaust process is measured, and the air-fuel ratio sensor in the exhaust pipe observes that the fuel ratio has dropped to keep this constant.
In the method of increasing the fuel ratio for the first time, the control of the combustion injection amount for two revolutions of the internal combustion engine is delayed.

According to the present invention, the amount of air taken into each cylinder before combustion is estimated, and fuel is injected in accordance with the variation in air distribution to each cylinder to suppress the variation in air-fuel ratio between cylinders. To realize highly accurate air-fuel ratio control with high responsiveness.

[0013]

According to the present invention, there is provided an injector for injecting fuel provided for each cylinder, a cylinder in an intake stroke is identified based on a crank angle, and a calculation program provided for each cylinder is provided. A fuel injection calculation for calling a calculation program corresponding to a cylinder in an intake stroke, estimating intake variation for each cylinder, and calculating a fuel injection amount to an injector of each cylinder in accordance with the estimated intake amount for each cylinder. And a processing device.

The present invention specifically provides the following devices.

The present invention measures the amount of air passing through a throttle in an air-fuel ratio control device for an internal combustion engine which has multiple cylinders and controls the ratio of the amount of air taken into each cylinder to the amount of fuel injected into the cylinder. An inflow air amount measuring device, an inflow air density measuring device for measuring the density of air in an intake manifold of an internal combustion engine, a crank angle sensor for measuring a crank angle of the internal combustion engine, and injecting fuel provided for each cylinder The injector and the cylinder in the intake stroke are identified on the basis of the crank angle, and a calculation program corresponding to the cylinder in the intake stroke is called from among the calculation programs provided for each cylinder, and the amount of air passing through the throttle and the intake manifold. The intake characteristic of each cylinder is estimated based on the air density and the crank angle of the cylinder, and an estimated value is obtained. Providing an air-fuel ratio control apparatus for an internal combustion engine having a fuel injection processing unit for calculating the fuel injection amount.

The intake characteristic is an intake amount or intake efficiency for each cylinder.

According to the present invention, in a method for estimating an inflow / intake amount of each cylinder of an internal combustion engine having multiple cylinders, a throttle passing air amount Mth is measured to obtain a gas density Pm in a manifold and a density increase ΔPm. By multiplying the increase amount △ Pm by the volume Md of the manifold (the volume of the area partitioned by the throttle and the intake valve), the increase amount 気 体 Mm of the gas in the manifold is calculated, and the crank angle is measured. Differentiation is performed to calculate the crank angular velocity, the intake efficiency q is calculated by the following equation as q = (Mth− △ Mm) / Md, and the intake air amount to each cylinder is calculated by the following equation Mc = Pm × (ω / 4π ) × Vc × q = Md × q (where 1 / C is the volume of the cylinder).

A method is provided for equalizing the intake air amount variation for each cylinder by estimating the inflow intake air amount for each cylinder and controlling the air-fuel ratio variation for each cylinder.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <Embodiment 1: Air-fuel ratio control based on cylinder-by-cylinder intake efficiency estimation> The configuration of the present invention will be described with reference to FIG.

The air taken in from outside the internal combustion engine passes through the throttle and is taken into the manifold 9. The torque generated from the internal combustion engine can be adjusted by adjusting the amount of air passing through according to the degree of opening of the throttle.

The air that has passed through the throttle fills the manifold 9, passes through a branch of the manifold 9, and is taken into the cylinder 5. An intake valve 7 is provided between the branch portion of the manifold 9 and the cylinder 5 and operates in conjunction with the crank angle. The intake valve 7 opens when the cylinder 5 is in an intake stroke, and air in the manifold 9 is supplied to the cylinder 5. Taken in.

The amount of air Mc thus taken into the cylinder 5
In order to measure the density of the air passing through the throttle 2 and the manifold 9, a density measuring instrument 1 for measuring the density of air in the manifold and a crank angle sensor 3 are attached to a collecting portion of the manifold 9.

The cylinder discriminating means 6 provided in the fuel injection arithmetic processing unit 100 discriminates the cylinder in the intake stroke based on the crank angle θ. Calculating means 601 to 60I for calculating the amount of air Mc flowing into the cylinder 5 (the i-th cylinder) and calculating the fuel injection amount Fi to the cylinder 5 based on the amount of air Mc.
(Where I is the number of cylinders) is prepared for each cylinder, and the one corresponding to the cylinder determined to be in the intake stroke by the cylinder determination means 6 is called.

In the called calculation means 60i, the intake efficiency ηi of the cylinder 5 (i is the number of a cylinder taking a value of 1 to I)
And the estimated intake efficiency ηi, the manifold density ρm measured by the density measuring device 1, and the crank rotation speed ω obtained by differentiating the output of the crank angle sensor 3.
From the intake air to the cylinder 5 is calculated.

Considering an ideal case where there is no flow loss when air is sucked into the cylinder 5 from the manifold 9, the amount Md of air flowing into the cylinder 5 is determined by setting the volume of the cylinder 5 to Vc.

[0026]

(Equation 1)

In practice, a flow loss occurs due to the shape of the manifold branching portion and the cylinder inlet, and the opening / closing timing of the intake valve 7. Therefore, the ratio of the flow into the cylinder as a result of the loss (this is the intake efficiency ηi )
The amount Mc of air actually flowing into the cylinder 5 is:

[0028]

(Equation 2)

Is calculated. Since the intake efficiency varies from cylinder to cylinder, precise control of the air-fuel ratio becomes possible by calculation for each cylinder. An example of a method of calculating the intake efficiency will be described later in [Calculation of the intake efficiency].

After the intake air amount Mc to the cylinder 5 is calculated in this manner, the fuel injection amount Fi to the cylinder is calculated from the calculated intake air amount Mc and the target air-fuel ratio λ.

[0031]

(Equation 3)

Calculate from the following. From the crank angle θ, the cylinder 5
The fuel injection timing is determined, and when the timing for injection is reached, the calculated injection amount Fi is injected from the injector 4.

FIG. 2 summarizes this operation procedure as a step diagram. First, the air amount M passing through the throttle
The th is measured (step 201), the density ρm of the gas in the manifold is measured (step 202), and the crank angle θ is measured (step 203). Based on the crank angle θ, it is determined whether or not the i-th cylinder 5 is in the intake stroke (step 204). If the i-th cylinder 5 is in the intake stroke, the i-th calculating means 60i is called (step 205), and the i-th cylinder intake efficiency estimating means 61i-61.
The intake efficiency ηi of the i-th cylinder 5 is calculated based on I, the throttle passing air amount Mth, the gas density ρm in the manifold, and the crank angular velocity ω obtained by differentiating the crank angle θ (step 206). From the intake efficiency ηi, the gas density ρm in the manifold 9 and the crank angular velocity ω, the intake air amount Mc to the i-th cylinder 5 is calculated based on the formula 2 (steps 207 to 62I). When the intake air amount Mc to the cylinder 5 is calculated, the fuel injection amount Fi to the cylinder is calculated based on the calculated amount Mc and the target air-fuel ratio λ according to Equation 3 (steps 208 to 63I) (step 208). When the crank angle θ becomes the angle θi at which fuel is injected into the cylinder 5 (steps 209 and 210), the i-th injector 4 injects the calculated amount of fuel (step 211).

As described above, the calculation means 601 to 6 are provided for each cylinder.
0I is provided, the intake efficiency for each cylinder is calculated, the intake air amount to the cylinder is calculated based on this, and the fuel injection amount to the cylinder is calculated. Precise control of the air-fuel ratio becomes possible.

[Calculation of Intake Efficiency] If the intake efficiency differs for each cylinder, even if the density ρm and the crank rotation speed ω in the manifold 9 are the same at the start of the intake stroke, the cylinder 9 flows into the cylinder 5 from the manifold 9. Since the air amount Mc is different, the change in the air density ρm in the manifold 9 and, consequently, the throttle passing air amount Mth depending on the density difference between the upstream and downstream of the throttle are different. Therefore, the intake efficiency is calculated from the air amount Mth passing through the throttle and the density ρm of the manifold 9 at 64i. When the air flow Mth passing through the throttle and the increase amount ΔMm of the air amount in the manifold 9 are used when the i-th cylinder 5 is in the intake stroke, FIG.
The amount of air Mci flowing into the i-th cylinder 5 is

[0036]

(Equation 4)

[0037]

(Equation 5)

Is calculated by From this and Equation 2, the intake efficiency ηi of the i-th cylinder is

[0039]

(Equation 6)

Can be calculated. This denominator has an intake efficiency of 1
And the inflow in an ideal case.
If you call it

[0041]

(Equation 7)

Is as follows.

It is known that the detection accuracy of the throttle passing air amount Mth is not very good. The intake efficiency ηi depends on the operating state of the internal combustion engine, in particular, the gas density ρm in the manifold 9 and the crank rotation speed ω, but since the change is gradual, the intake efficiency ηi obtained by Equation 6 is obtained.
Is smoothed (65i), the accuracy of the intake efficiency estimation can be improved. The smoothed intake efficiency ηi is stored in the intake efficiency memory 66i.

The calculation procedure of the intake efficiency ηi will be described with reference to FIG.

First, the throttle passing air amount Mth is measured (step 401). Next, the density ρm of the gas in the manifold 9 is obtained by the density measuring means 1, and the increase Δρ
By multiplying m by the volume of the manifold 9 (the volume of the area partitioned by the throttle and the intake valve 7), the amount of increase ΔMm of the gas in the manifold 9 is calculated (step 402).

Thereafter, the crank angle θ is measured and differentiated to calculate the crank angular velocity ω. From this and the density ρm of the gas in the manifold 9, the ideal inflow Md into the cylinder i is calculated by the equation (1). (Step 403). Based on these calculation results, the intake efficiency ηi is calculated based on Equation 6 (step 404).

The intake efficiency ηi when the cylinder 5 was in the intake stroke last time is read from the intake efficiency memory 66i (step 405), and a weighted average of the previously obtained intake efficiency ηi and the current intake efficiency ηi is obtained. Then, the intake efficiency ηi is smoothed (step 406).

By obtaining the intake efficiency ηi in this manner, the intake efficiency for each cylinder can be obtained with high accuracy, adapting to the variation for each cylinder.

[Measurement of Density] As a specific sensor for measuring the density of gas, use of a combination of a pressure sensor and a temperature sensor is mentioned as an example. From the definition of density and the equation of state of the gas,

[0050]

(Equation 8)

Therefore, the density ρ can be obtained by dividing the gas pressure P by the temperature T and correcting the unit by the gas constant R. In order to measure the density of the manifold 9 as in the present embodiment, as shown in FIG. 5, the pressure sensor 11 and the temperature sensor 12 are arranged at the gathering portion of the manifold 9, and the calculation is performed in the calculation means 60 according to the equation (8). Then, the density ρm of the gas in the manifold 9 is obtained.

[Measurement of Throttle Passing Air Amount 1] FIG. 6 shows an example of a specific sensor configuration for obtaining the air amount Mth passing through the throttle. The air amount Mth passing through the throttle is determined by the pressures Pa and Pm upstream and downstream of the throttle, the temperatures Ta and Tm, and the throttle opening α. How to find it

[0053]

(Equation 9)

Is introduced in a book on hydrodynamics (for example, Kazuyasu Matsuo, “Compressible Fluid Dynamics”, p. 6).
4). Here, 13 is a throttle opening sensor, 14 is a pressure sensor, and 15 is a temperature sensor.

Accordingly, the procedure for obtaining the amount of air Mth passing through the throttle using the sensor having the configuration shown in FIG. 6 will be described with reference to FIG. 7. The external pressure Pa is measured by the pressure sensor 14 disposed upstream of the throttle. Measure (Step 70
1) The manifold pressure Pm is measured by the pressure sensor 11 disposed downstream of the throttle (step 702), and the outside air temperature Ta is measured by the temperature sensor 15 disposed upstream of the throttle (step 703). The manifold temperature Tm is measured by the temperature sensor 12 (step 704), the throttle opening α is measured by the throttle opening sensor 13 (step 705), and the amount of air passing through the throttle Mth is calculated by using the equation 9 in the calculating means 60. It may be obtained (step 706).

[Measurement 2 of Throttle Passing Air Amount] As another method of measuring the throttle passing air amount Mth, there is a method using a hot wire air flow meter. The hot-wire air flow meter is described in Japanese Patent Application Laid-Open No. 9-16664, etc.
The purpose is to measure the flow rate of the gas based on the amount of heat taken from the hot wire when the gas passes through the cross section where the hot wire is arranged. In the embodiment of the present invention, as shown in FIG. 8, the hot-wire type air flow meter 16 is arranged upstream of the throttle, and the measurement data is read by the calculating means 60 to measure the throttle passing air amount Mth.

The density measuring means 1 and the throttle passing air amount measuring means 2 are provided, and the calculating means 601 to 601 are provided for each cylinder.
60I, the intake efficiency for each cylinder is calculated, the intake air amount Mc to the cylinder is calculated based on the calculated intake efficiency, and the fuel injection amount to the cylinder is calculated. Thus, precise control of the air-fuel ratio becomes possible.

<Embodiment 2: Air-fuel ratio control using a cylinder-by-cylinder variation correction coefficient> The intake efficiency changes gradually depending on the operating state of the internal combustion engine. In [Calculation of intake efficiency], the intake efficiency obtained from the present measurement data was smoothed by taking a weighted average with the past intake efficiency to improve the accuracy. Depending on how it is applied, it may be conceivable that it cannot follow the change in intake efficiency.

In the case of the same type of internal combustion engine, it is considered that there is not much difference between the shapes of the functions of the intake efficiency depending on the individual and the shapes of the functions of the intake efficiency depending on the cylinder. If the intake efficiency of the first cylinder, the intake efficiency of the second cylinder, and the common intake efficiency indicating the average intake efficiency of all cylinders are graphed as a function of the density of the gas in the manifold, for example, FIG.
9A, the correction coefficient obtained by dividing the intake efficiency of each cylinder by the common intake efficiency is, for example, as shown in FIG.
It is considered that the function becomes a gentle function near 0. Therefore, a common intake efficiency map is prepared in advance for a dynamic portion that changes depending on the operation state of the internal combustion engine, and a scale parameter portion that changes for each cylinder and each individual internal combustion engine is estimated as a correction coefficient, and a common intake efficiency map is obtained. By multiplying the efficiency map and the correction coefficient for each cylinder, the intake efficiency follows the change in intake efficiency due to changes in the operating state of the internal combustion engine, and can also respond to variations in intake efficiency for each cylinder and individual internal combustion engine. The estimating means will be described.

FIG. 10 shows the configuration. 1 are given the same reference numerals, and description thereof will not be repeated. As compared with the air-fuel ratio control device shown in FIG. 1, an intake efficiency map 21 common to all cylinders is newly prepared, and intake efficiency estimating means 611 to 61I corresponding to each cylinder is different.

The intake efficiency estimating means 61i of the i-th cylinder 5
The correction coefficient calculating means 67i for estimating the correction coefficient Ci from the throttle passing air amount Mth, the air density Mth of the manifold 9 and the crank angular velocity ω, and the correction coefficient Ci when the cylinder 5 was in the intake stroke last time is stored. And a correction coefficient memory 69i for storing a result obtained by taking a weighted average with a correction coefficient Ci obtained from the current measurement data.
Smoothing means 65i for calculating the weighted average, and intake air for calculating a corrected intake efficiency ηi in which a difference for each cylinder has been corrected from the obtained correction coefficient Ci and the intake efficiency η0 read from the intake efficiency map 21. And efficiency correcting means 68i.

In the air-fuel ratio control apparatus shown in FIG. 10, the parts other than the intake efficiency estimating means 611 to 61I are completely the same as those in FIG. 1, and the operation of the intake efficiency estimating means 61i will be described here.

The intake efficiency ηi is defined as the product ηi = η of a component η0, which is common to all cylinders and varies according to the operating state of the internal combustion engine, and a scale factor component Ci due to variations among the cylinders.
Assuming 0 × Ci, from equation 6,

[0064]

(Equation 10)

The right side of Equation 6 is represented by the intake efficiency map 2
By dividing by 1 the common intake efficiency η0 read from 1, the component that changes depending on the operating state is removed, and a correction coefficient Ci that takes a substantially constant value for each cylinder is obtained.

After smoothing this, the intake efficiency map 2
By reading and multiplying the common intake efficiency η0 from 1 according to the operating state and multiplying the same, the intake efficiency ηi in which the variation among the cylinders is corrected can be obtained.

The procedure for estimating the intake efficiency ηi in the intake efficiency estimating means 61i will be described with reference to the step diagram of FIG.

First, the throttle passing air amount Mth is measured (step 1101). Next, the amount of increase ΔMm of the gas in the manifold 9 is calculated from the density ρm of the gas in the manifold 9 measured by the density measuring means 1 (step 1102).

Thereafter, the ideal inflow Md into the cylinder i is calculated from the crank angular velocity ω and the gas density ρm in the manifold 9 by the equation (1) (step 1103), and the intake efficiency map 21 is calculated according to the operating state of the internal combustion engine. From the common intake efficiency η0
Is read (step 1104). Based on these calculation results, a correction coefficient Ci is calculated on the basis of Expression 10 (step 1105).

The correction coefficient Ci when the cylinder was in the intake stroke last time is read from the correction coefficient memory 21 (step 1106), and the weighted average of the correction coefficient Ci obtained last time and the current correction coefficient Ci is obtained. , And smoothes the correction coefficient Ci (step 1107).

By multiplying the correction coefficient Ci by the common intake efficiency η0, the intake efficiency ηi is obtained (step 110).
8).

As described above, the intake efficiency ηi is divided into the common intake efficiency η0 which varies depending on the operation state of the internal combustion engine and the correction coefficient Ci which depends on the cylinder.
Prepares a map in advance, and estimates the correction coefficient Ci at the time of operation, thereby obtaining an intake efficiency that differs for each cylinder with high accuracy and quickly following a change in intake efficiency due to a change in the operating state of the internal combustion engine. be able to.

<Embodiment 3: Air-fuel ratio control providing a fuel injection amount map for each cylinder> In <Invention 1>, the intake efficiency is estimated while the internal combustion engine is operating. The combustion injection amount was calculated based on
An air-fuel ratio control device that prepares a map of the relationship between sensor data and fuel injection amount for each cylinder, controls the fuel injection amount for each cylinder by searching this map, and precisely controls the air-fuel ratio for each cylinder is also available. Conceivable. An advantage of such a device is that even if the calculation means mounted on the air-fuel ratio control device has a low calculation performance, highly accurate cylinder-by-cylinder air-fuel ratio control can be realized.

The configuration of the air-fuel ratio control device will be described with reference to FIG. The method for creating the map will be described later in [Creation of Fuel Injection Amount Map].

The configuration of this device is different from that of the air-fuel ratio control device shown in FIG. 1 in that the calculation means 601 to 60 provided in each cylinder are provided.
I is different. The calculation means 601 to 60I are based on the fuel injection amount maps 711 to 71I indicating the relationship between the measurement data and the fuel injection amount for each cylinder, the throttle passing air amount Mth, the gas density ρm in the manifold, and the crank angular velocity ω. It comprises fuel injection amount calculation means 701 to 70I for reading the fuel injection amount from the fuel injection amount maps 711 to 71I and sending an injection amount command to the injector 4.

The operation procedure of the air-fuel ratio control device provided with such calculation means 601 to 60I for each cylinder will be described with reference to FIG.

First, the amount of air Mth passing through the throttle is measured (step 1201), the density ρm of the gas in the manifold is measured (step 1202), and the crank angle θ is measured (step 1203). It is determined whether or not the i-th cylinder 5 is in the intake stroke based on the crank angle θ (step 1204). If the i-th cylinder 5 is in the intake stroke, the i-th calculation means 60i is called (step 1205).

When the i-th calculation means is called, the fuel injection amount calculation means 70i searches the fuel injection amount map 71i based on the throttle passing air amount Mth, the gas density ρm in the manifold, and the crank angular velocity ω. Then, the fuel injection amount Fi to the i-th cylinder is obtained (step 1206). When the crank angle θ becomes the angle θi at which fuel is injected into the cylinder 5 (steps 1207 and 1208), the i-th injector injects the calculated amount Fi of fuel (step 120).
9).

[Creation of Fuel Injection Amount Map] An apparatus for creating the fuel injection amount maps 711 to 71I is shown in FIG.
4 will be described.

In order to generate the fuel injection amount maps 711 to 71I, a throttle control device 1401 for controlling the throttle opening air amount Mth by controlling the opening degree of the throttle of the internal combustion engine, and a load attached to the crank to apply a load. Generator 1 that adjusts the rotational speed ω of the crank
402, a fuel injection amount is calculated based on sensor data from the throttle passing air amount measuring device 2, the manifold pressure measuring device 1, and the crank angle sensor 3, and the relationship between these sensor data and the fuel injection amount is represented by a fuel injection amount map. A fuel injection amount map creating device 1403 for recording 711-71I is used.

The operation procedure of the fuel injection amount map creating device 1403 will be described with reference to FIG.

First, a fuel injection amount map creating device 1403
Indicates that the throttle opening command value is
01 (step 1501), and the load applied to the crank is sent to the load generating means 1402 (step 150).
2). This sets the operating state of the internal combustion engine,
Various throttle flows Mth, manifold density ρm,
The crank angular velocity ω can be realized. The throttle passing air amount M of the internal combustion engine in which the operation state is set in this manner
th (step 1503), manifold density ρm (step 1504), crank angle θ (step 1505)
Is read by the fuel injection map creating device 1403. The fuel injection map creation device 1403 determines which cylinder is in the intake stroke based on the read crank angle θ.
(Step 1506). Based on this determination result, the calculation of the intake efficiency ηi of the cylinder 5 in the intake stroke is performed in the fuel injection map creator 1403 (step 1507).
The calculation method of the intake efficiency ηi is described in [Calculation of intake efficiency] described above.
Is the same as Subsequent to the calculation of the intake efficiency ηi, the calculation of the air amount Mc flowing into the cylinder 5 (step 1508),
Calculation Fi of the fuel injected into the cylinder 5 (step 1509)
I do. This calculation method is the same as that described in << Embodiment 1 of the invention >>. Based on the calculated fuel injection amount Fi, the fuel injection map creating device 1403 sends a fuel injection command to the injector 4 of the cylinder 5, and the injector 4 injects fuel (step 1510). At this time, the set of the throttle passing air amount Mth, the manifold density ρm, the crank angular velocity ω, and the fuel injection amount Fi are stored in the fuel injection amount map creation device 1403 for each cylinder (step 1511). When a sufficient amount of measurement data and injection amount set are stored, these data are interpolated to create a map for searching the fuel injection amount from the throttle passing air amount Mth, the manifold density ρm, and the crank angular velocity ω. The map is created for each fuel injection amount map 711 to 71I in the air-fuel ratio control device (step 151).
3). If a sufficient set of the measurement data and the injection amount is not stored, the process returns to step 1501 to further collect data.

As described above, the calculation of the fuel injection amount in << Embodiment 1 >> is performed by the fuel injection amount map creating device 1403 prepared separately from the air-fuel ratio control device, and the result is stored in the air-fuel ratio control device. In the actual operation, the map is searched to control the fuel injection amount by searching this map, thereby reducing the calculation load of the calculation means 601 to 60I in the air-fuel ratio control device. Precise air-fuel ratio control corresponding to the variation in intake efficiency for each cylinder can be performed while suppressing this.

[0084]

The air-fuel ratio in the cylinder can be precisely controlled by measuring the amount of air taken into the cylinder and controlling the fuel injection amount while estimating the intake efficiency that differs for each engine or cylinder. . This can contribute to improving the fuel efficiency of the internal combustion engine and reducing harmful substances in the exhaust gas.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a configuration according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an operation procedure according to the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between an increase and a decrease in the amount of air in the embodiment of the present invention.

FIG. 4 is a diagram showing an example of a procedure for estimating intake efficiency according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a sensor configuration for density measurement according to the embodiment of the present invention.

FIG. 6 is a diagram showing an example of a sensor configuration for measuring the amount of air passing through a throttle according to the embodiment of the present invention.

FIG. 7 is a diagram showing an example of a calculation procedure of a throttle passing air amount according to the embodiment of the present invention.

FIG. 8 is a diagram showing another example of a sensor arrangement for measuring the amount of air passing through the throttle according to the embodiment of the present invention.

FIG. 9 is a diagram illustrating an example of a diagram illustrating a variation in intake efficiency for each cylinder and a change in intake efficiency depending on an operating state;

FIG. 10 is a diagram showing an example of an embodiment using a common intake efficiency map of the present invention.

FIG. 11 is a diagram showing an example of an operation procedure of an embodiment using a common intake efficiency map of the present invention.

FIG. 12 is a diagram showing an example of an embodiment in which a cylinder-by-cylinder intake efficiency map of the present invention is prepared in advance.

FIG. 13 is a diagram showing an example of an operation procedure of an embodiment of preparing an intake efficiency map for each cylinder in advance according to the present invention.

FIG. 14 is a diagram showing an example of means for preparing an intake efficiency map for each cylinder in advance according to the present invention.

FIG. 15 is a diagram showing an example of a procedure for preparing an intake efficiency map for each cylinder in advance according to the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 366 F02D 45/00 366E 366F 366B F-term (Reference) 3G084 AA03 BA09 BA13 BA15 DA25 EA05 EB02 EB25 FA02 FA07 FA08 FA10 FA11 FA38 3G301 HA04 HA06 JA02 JA21 MA01 MA12 MA18 NA02 NA05 NB02 NB03 NC02 PA01Z PA04Z PA07Z PA10Z PA11Z PE03Z PE05Z

Claims (12)

[Claims] 1. An air-fuel ratio control device for an internal combustion engine, comprising: a plurality of cylinders, for controlling a ratio of an amount of air taken into each cylinder to a fuel injected into the cylinder. The cylinders in the intake stroke are identified based on the crank angle, a calculation program corresponding to the cylinder in the intake stroke is called from among the calculation programs provided for each cylinder, and the intake variation for each cylinder is estimated by An internal combustion engine comprising: a fuel injection arithmetic processing unit that specifies an intake air amount for each cylinder, and calculates a fuel injection amount to an injector of each cylinder in accordance with the estimated intake air amount for each cylinder. Air-fuel ratio control device. 2. An air-fuel ratio control system for an internal combustion engine having a multi-cylinder system for controlling the ratio of the amount of air taken into each cylinder to the amount of fuel injected into the cylinder. An air amount measuring device, an air density measuring device for measuring the density of air in an intake manifold of the internal combustion engine, a crank angle sensor for measuring a crank angle of the internal combustion engine, and an injector for injecting fuel provided for each cylinder, The cylinders in the intake stroke are identified based on the crank angle, and the calculation program corresponding to the cylinder in the intake stroke is called from among the calculation programs provided for each cylinder, and the amount of air passing through the throttle, An intake value is estimated for each cylinder based on the density and the crank angle to obtain an estimated value, and fuel is injected into an injector of each cylinder in accordance with the estimated value. Air-fuel ratio control system for an internal combustion engine, characterized in that a fuel injection processing unit for calculating the. 3. The air-fuel ratio control apparatus for an internal combustion engine according to claim 2, wherein the intake characteristic is an intake amount or intake efficiency for each cylinder. 4. The fuel injection control device according to claim 2, wherein a ratio of a loss when air is taken into each cylinder based on an amount of air passing through a throttle, a density of air in an intake manifold, and a crank angle speed. Is calculated for each cylinder, the amount of air taken into the cylinder is calculated from the rate of this loss, the density of air in the manifold and the speed of the crank angle, and the fuel injection amount to the cylinder is calculated. Air-fuel ratio control device. 5. The fuel injection control device according to claim 2, wherein a loss when air is taken into each cylinder is determined based on an amount of air passing through a throttle, a density of air in an intake manifold, and a crank angle speed. The ratio is calculated for each cylinder, and the loss ratio is divided by a common intake efficiency provided in common for all cylinders to calculate a correction coefficient representing a variation for each cylinder, and weighted with the previous correction coefficient for the cylinder. An air-fuel ratio control device characterized in that a correction coefficient is smoothed by taking an average, and a ratio of a loss corrected for each cylinder is calculated by multiplying the smoothed correction coefficient by a common intake efficiency. 6. The method according to claim 2, wherein the amount of air used to fill the manifold is calculated from the change in the density of the gas in the manifold, and the loss of the gas flow is calculated from the density of the gas in the manifold and the crank angular velocity. Calculate the theoretical amount of air flowing into the cylinder when it is set to 0, subtract the amount of air used to fill the manifold from the amount of air that has passed through the throttle, and divide the result by the amount of theoretical inflow air to obtain the intake efficiency. An air-fuel ratio control device for an internal combustion engine, which calculates and takes a weighted average with a previous intake efficiency to smooth the intake efficiency. 7. The method according to claim 3, wherein the amount of air used to fill the manifold is calculated from the change in the gas density of the manifold, and the gas flow loss is calculated from the gas density in the manifold and the crank angular velocity. Calculate the theoretical amount of air flowing into the cylinder when it is set to 0, subtract the amount of air used to fill the manifold from the amount of air that has passed through the throttle, and use the result as the theoretical amount of air that is common to each cylinder. The correction coefficient was calculated by dividing by the product of the intake efficiency, the correction coefficient was smoothed by taking the weighted average with the previous correction coefficient, and the correction coefficient was corrected for each cylinder by multiplying the smoothed correction coefficient by the common intake efficiency. An air-fuel ratio controller that calculates intake efficiency. 8. The air-fuel ratio of an internal combustion engine according to claim 2, wherein the fuel injection arithmetic processing unit includes a fuel injection amount map, and calculates the fuel injection amount using the fuel injection amount map. Control device. 9. The air-fuel ratio control device for an internal combustion engine according to claim 2, wherein the inflow air density measuring device comprises a pressure sensor and a temperature sensor disposed in a manifold. 10. The apparatus according to claim 2, wherein the inflow air density measuring device comprises a pressure sensor and a temperature sensor disposed in the manifold, and an opening sensor for measuring an opening of a throttle. Control device for an internal combustion engine. 11. An air-fuel ratio control device for an internal combustion engine according to claim 2, wherein said inflow air density measuring device comprises a hot wire air flow meter. 12. A method for estimating an inflow / intake air amount for each cylinder of an internal combustion engine having multiple cylinders, wherein a throttle passing air amount Mth is measured to obtain a density Pm of gas in the manifold and an increase ΔPm of the density. The increase amount ΔPm is multiplied by the manifold volume Md (the volume of the area partitioned by the throttle and the intake valve) to calculate the increase amount ΔMm of the gas in the manifold, and the crank angle is measured and differentiated. Calculate the crank angular velocity by using the following formula, and calculate the intake efficiency q by q = (Mth−ＭMm) / Md, and calculate the intake air amount to each cylinder by the following formula: Mc = Pm × (ω / 4π) × Vc × q = Md × q (where 1 / C is the volume of the cylinder).