JPH1151866A - Air fuel ratio detector of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect an air fuel ratio even in the case where fuel different in an absorption coefficient is used for an internal combustion engine. SOLUTION: The detector is provided with a device 7 for projecting light of wavelength in which fuel vapor is selectively absorbed from the light emission side of the air fuel ratio measuring part of a combustion chamber to the light receiving side, and detecting intensity of light transmitting the fuel vapor of the combustion chamber, and a calculation means 15 for finding an air fuel ratio prior to ignition on the basis of output of the device 7 and the absorption coefficient of fuel. A detector 23 for detecting the absorption coefficient of fuel on use, and a correction device 25 for replacing the absorption coefficient on use in the calculation device 15 with the same or substantially the same as the absorption coefficient newly detected by the detector 23 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting an air-fuel ratio of a combustion chamber before ignition in an internal combustion engine such as a gasoline engine.

[0002]

2. Description of the Related Art An air-fuel ratio detecting device of this type is disclosed in
As disclosed in Japanese Patent Publication No. 288283, a gasoline engine is provided with a light source that emits light of a wavelength that gasoline vapor selectively absorbs, and a light intensity detection element that detects the intensity of light of that wavelength. An air-fuel ratio measurement unit is provided near the ignition plug in the chamber, and an optical path is provided to project the light emitted from the light source from the light-emitting side of the air-fuel ratio measurement unit to the light-receiving side and make it incident on the light intensity detection element, thereby detecting transmitted light intensity. Make up the device.

In a transmitted light intensity detecting device, light having a wavelength selectively absorbed by gasoline vapor passes through a gasoline vapor / air mixture present between a light emitting side and a light receiving side of an air-fuel ratio measuring section. Then, the intensity of the transmitted light absorbed and attenuated by the gasoline vapor is detected.

[0004] The concentration C of gasoline is obtained from the following relational expression.

C = ln (I ₀ / I) / (μ · L) where ln is a natural logarithm. I ₀ is the intensity of light incident on gasoline vapor, and I is the intensity of light transmitted through gasoline vapor. μ is the extinction coefficient of gasoline vapor. L is the optical path length of the air-fuel ratio measurement unit.

Further, a device for detecting the pressure in the combustion chamber is provided in order to determine the air density in the combustion chamber.

[0007] An air-fuel ratio calculating device is provided in which the relationship between the intensity of the transmitted light, the pressure in the combustion chamber, and the air-fuel ratio is measured in advance, a map for calculating the air-fuel ratio is prepared, and the air-fuel ratio calculation map is stored. ing.

In the air-fuel ratio calculation device, the air-fuel ratio in the vicinity of the ignition plug of the combustion chamber before ignition is obtained based on the output of the transmitted light intensity detection device and the output of the combustion chamber pressure detection device and the air-fuel ratio calculation map.

The fuel injection timing is controlled based on the air-fuel ratio.

[0010]

However, in the above-described air-fuel ratio detecting device, the extinction coefficient of gasoline vapor varies depending on a gasoline manufacturing plant, a production lot, and types such as regular gasoline and premium gasoline. Rather, it is assumed that it is uniquely determined.

In the case of a single component fuel such as propane or methane, the extinction coefficient of the single component fuel does not change depending on the fuel manufacturer or production lot and is determined uniquely. Even if fuel of a different production lot is supplied during operation, no error occurs in the air-fuel ratio detected by the air-fuel ratio detecting device.

However, multi-component fuels such as gasoline have different compositions depending on factories, production lots, types such as regular gasoline and premium gasoline, or seasons. Not determined. For example, there is a difference of about 20% in the extinction coefficient between regular gasoline and premium gasoline.

Therefore, in a multi-component fueled internal combustion engine, if a fuel having an absorption coefficient different from the absorption coefficient preset in the air-fuel ratio detector is used, an error occurs in the air-fuel ratio detected by the air-fuel ratio detector.

Then, errors occur in the fuel injection timing and the ignition timing controlled based on the air-fuel ratio detected by the air-fuel ratio detection device.

[0015]

In order to solve the above problems, first, at any time, the extinction coefficient of the fuel used in the multi-component fueled internal combustion engine is detected. It is necessary to calculate the air-fuel ratio using the newly detected extinction coefficient instead of the extinction coefficient in use. At the time of operation in which the air-fuel mixture in the combustion chamber is uniform, the air-fuel ratio near the ignition plug in the combustion chamber is the same as the overall air-fuel ratio in the combustion chamber. At this time, the air-fuel ratio near the ignition plug in the combustion chamber is detected. The air-fuel ratio detecting device measures the transmitted light intensity, and the air-fuel ratio sensor that detects the entire air-fuel ratio of the combustion chamber from the exhaust gas of the exhaust pipe determines the overall fuel concentration of the combustion chamber.

Substituting the overall fuel concentration C of the combustion chamber determined by the air-fuel ratio sensor and the transmitted light intensity I detected by the air-fuel ratio detector into the following equation, which is a modification of the above-described relational equation,
Calculate the absorption coefficient μ of the fuel in use.

Μ = ln (I ₀ / I) / (CL) The newly detected extinction coefficient is compared with the extinction coefficient used in the air-fuel ratio calculator, and when the two are different or the difference between the two. Exceeds a certain range, the air-fuel ratio calculation device calculates the air-fuel ratio using the newly detected absorption coefficient instead of the currently used absorption coefficient. Or
From a plurality of absorption coefficients stored in the air-fuel ratio calculation device,
Select the extinction coefficient closest to the newly detected extinction coefficient,
In the air-fuel ratio calculation device, instead of the extinction coefficient in use,
The air-fuel ratio is calculated using the newly selected extinction coefficient.

Then, the air-fuel ratio is detected based on the extinction coefficient which is the same as or substantially the same as the extinction coefficient of the fuel being used in the multi-component fuel internal combustion engine. For example, in a direct-injection gasoline engine that directly injects gasoline as fuel into the combustion chamber, the fuel-air mixture in the combustion chamber is not uniform when injecting fuel in the compression stroke. The time from ignition to ignition is long, during which fuel diffuses and intake air flows, and immediately before ignition, the mixture in the combustion chamber becomes uniform.

Therefore, immediately before ignition when fuel is injected in the intake stroke, the air-fuel ratio detecting device and the air-fuel ratio sensor are used to detect the extinction coefficient of the fuel in use.

When fuel is injected during the intake stroke, the fuel is often burned at a stoichiometric air-fuel ratio. In such a case, instead of the air-fuel ratio sensor, an O ₂ sensor that detects the combustion state of the combustion chamber at the stoichiometric air-fuel ratio from the exhaust gas of the exhaust pipe may be used.

[0021]

SUMMARY OF THE INVENTION According to the present invention, light having a wavelength which fuel vapor selectively absorbs is projected from a light emitting side of an air-fuel ratio measuring section provided in a combustion chamber to a light receiving side, and the combustion chamber has A transmitted light intensity detector for detecting the intensity of light transmitted through a mixture of fuel vapor and air; and an air for obtaining an air-fuel ratio before ignition of a combustion chamber based on an output of the transmitted light intensity detector, an absorption coefficient of fuel, and the like. An air-fuel ratio detection device for an internal combustion engine provided with a fuel ratio calculation device, wherein an absorption coefficient detection device for detecting an absorption coefficient of a fuel used in the internal combustion engine, and an absorption coefficient used for the air-fuel ratio calculation device, an absorption coefficient detection device An extinction coefficient correction device was used to replace the extinction coefficient with or substantially the same as the extinction coefficient newly detected.

[0022]

The air-fuel ratio of the combustion chamber before ignition is detected based on the same or almost the same extinction coefficient as that of the fuel used in the internal combustion engine. Therefore, even if fuel having an absorption coefficient different from that of the fuel being used is supplied during operation, an error is hardly generated in the detected value of the air-fuel ratio.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Example (see FIGS. 1 to 3)> This example is an apparatus for detecting an air-fuel ratio in the vicinity of a combustion chamber spark plug before ignition in a gasoline engine.

As shown in FIGS. 1 and 2, the air-fuel ratio detecting device includes a light source 1 which emits light having a wavelength which gasoline vapor selectively absorbs, and a light intensity detecting device which detects the intensity of the light having the wavelength. An element 2 is provided, and an air-fuel ratio measuring unit 5 is provided near a spark plug 4 in a combustion chamber 3 of a gasoline engine, and light emitted from the light source 1 is projected from the light-emitting side of the air-fuel ratio measuring unit 5 to a light receiving side. An optical path 6 for entering the detection element 2 is provided, and an air-fuel ratio measuring unit 5 is provided.
The transmitted light intensity detecting device 7 detects the intensity of light transmitted through a mixture of gasoline vapor and air existing between the light emitting side and the light receiving side.

The light source 1 is an infrared laser emitting infrared light having a wavelength of 3.39 μm. The light intensity detection element 2 is a photoelectric conversion element. The optical path 6 includes a half mirror 8 and an optical fiber 9.

As shown in FIG. 3, the air-fuel ratio measuring unit 5 is connected to the ignition plug 4 by the tip of an optical fiber 9 and the optical window 1 connected thereto.
0, and the optical window 10 is arranged so as to face the bent tip of the cathode electrode 12 close to the tip of the anode electrode 11 of the ignition plug 4. And reflected by the bent tip of the cathode electrode 12, and the reflected light passes through the mixture in the combustion chamber 3 and enters the optical window 10.

Further, as shown in FIG. 1, an air-fuel ratio calculating device 15 is provided, and the light intensity detecting element 2 of the transmitted light intensity detecting device 7 is connected to this. A combustion chamber air density detecting device 16 is provided and connected to the air-fuel ratio calculating device 15. The combustion chamber air density detector 16 calculates the air density of the combustion chamber 3 from the intake air amount of the combustion chamber 3 detected from the pressure of the intake pipe of the gasoline engine and the volume of the combustion chamber 3 detected from the crank angle of the gasoline engine. Things. It should be noted that this may be for obtaining the air density of the combustion chamber 3 from the pressure of the combustion chamber 3.

A fuel injection timing control device 17 and an ignition timing control device 18 are provided.
Are connected.

The air-fuel ratio calculator 15 stores the absorption coefficient of gasoline vapor and the like, and stores the transmitted light intensity detector 7
The air-fuel ratio of the air-fuel ratio measurement unit 5 is determined based on the output of the combustion chamber air density detector 16 and the like. That is, the gasoline concentration is determined from the absorption coefficient of gasoline vapor and the intensity of transmitted light, and the air density in the combustion chamber 3 is divided by the gasoline concentration to obtain
An air-fuel ratio before ignition in the vicinity of the ignition plug 4 in the combustion chamber 3 is obtained.

This air-fuel ratio is determined by the fuel injection timing control device 17.
To the ignition timing control device 18 to control the fuel injection timing and the ignition timing of the gasoline engine, respectively.

An exhaust pipe 21 of a gasoline engine is provided with an air-fuel ratio sensor 22, as shown in FIG. Note that this may be an O ₂ sensor. Further, as shown in FIG. 1, an absorption coefficient detecting device 23 is provided, and the air-fuel ratio sensor 22 and the air-fuel ratio calculating device 15 are connected to this.

In the extinction coefficient detecting device 23, the output of the transmitted light intensity detecting device 7 and the total amount of the combustion chamber 3 obtained from the exhaust gas by the air-fuel ratio sensor 22 during the operation in which the air-fuel mixture in the combustion chamber 3 becomes uniform are measured. The extinction coefficient of the gasoline vapor in use is determined based on the fuel concentration and the like.

As shown in FIG. 1, an extinction coefficient comparing device 24 is provided, to which an extinction coefficient detecting device 23 and an air-fuel ratio calculating device 15 are connected.

In the extinction coefficient comparison device 24, the extinction coefficient newly detected by the extinction coefficient detection device 23 is compared with the extinction coefficient used in the air-fuel ratio calculation device 15, and when the two are different or the difference between the two is obtained. Output when exceeding a certain range.

As shown in FIG. 1, an extinction coefficient correction device 25 is provided, and an extinction coefficient comparison device 24 and an air-fuel ratio calculation device 15 are connected to the extinction coefficient correction device 25, respectively. Connected.

In the extinction coefficient correction unit 25, when the extinction coefficient comparison unit 24 outputs, the extinction coefficient used in the air-fuel ratio calculation unit 15 is replaced by the extinction coefficient newly detected by the extinction coefficient detection unit 23. Alternatively, an absorption coefficient closest to the absorption coefficient newly detected by the absorption coefficient detection device 23 is selected from the plurality of absorption coefficients stored in the air-fuel ratio calculation device 15, and the absorption coefficient used in the air-fuel ratio calculation device 15 is selected. Replace the coefficient with the newly selected extinction coefficient.

Then, the air-fuel ratio calculation device 15 calculates the air-fuel ratio using the newly obtained absorption coefficient. That is, the air-fuel ratio is detected based on the absorption coefficient that is the same as or substantially the same as the absorption coefficient of the gasoline being used in the gasoline engine.

<Second Example (See FIGS. 4 and 5)> In this example, the air-fuel ratio detecting device of the first example is heated and emits light to eliminate the need for the light source 1 such as an infrared laser. The light source is a metal, which is incorporated in the ignition plug 4.

As shown in FIG. 4, the ignition plug 4
The heating element 32 is fixed to the inner surface of the bent end of the cathode electrode 12, and the resistance wire in the heating element 32 and the end of the electric wire 31 are connected. The end of the electric wire 31 protruding from the ignition plug 4 is connected to a power supply 33.

The heating element 32 embeds a resistance wire in a filler,
The filler is covered with a sheet metal. When the resistance wire is energized, the thin metal sheet of the coating material is heated and emits light having a wavelength from the visible region to the infrared region.

This light is directed to the heating plug 32 and
Into the optical window 10 buried in the device. Optical window 1
As shown in FIG. 5, light having a wavelength selectively absorbed by gasoline vapor, such as infrared light having a wavelength of 3.39 μm, is provided between the optical fiber 9 and the light intensity detecting element 2 connected to the optical fiber 9. An optical filter 34 that transmits light is provided.

The other points are the same as in the first example.

<Third Example (See FIGS. 6 and 7)> In this example, the optical filter 34 and the light intensity detecting element 2 are ignited in the air-fuel ratio detecting device of the second example in order to make the optical fiber 9 unnecessary. It is built into the stopper 4.

The ignition plug 4 is, as shown in FIG.
The optical filter 34 is embedded on the rear side of the optical filter 3.
4, the light intensity detecting element 2 is buried behind the light intensity detecting element 2, and the tip of the electric wire 35 is buried behind the light intensity detecting element 2.
And the end of the electric wire 35.

The end of the electric wire 35 protruding from the ignition plug 4
As shown in FIG. 7, it is configured to be connected to the air-fuel ratio calculation device 15.

The other points are the same as in the second example.

[Brief description of the drawings]

FIG. 1 is a block diagram of an air-fuel ratio detection device according to a first example of an embodiment of the present invention.

FIG. 2 is a system schematic diagram of the air-fuel ratio detection device of the same example.

FIG. 3 is a vertical sectional view of an ignition plug of the air-fuel ratio detection device of the same example.

FIG. 4 is a longitudinal sectional view of an ignition plug of an air-fuel ratio detection device according to a second example of the embodiment.

FIG. 5 is a system schematic diagram of the air-fuel ratio detection device of the same example.

FIG. 6 is a longitudinal sectional view of an ignition plug of an air-fuel ratio detection device according to a third example of the embodiment.

FIG. 7 is a system schematic diagram of the air-fuel ratio detection device of the same example.

[Explanation of symbols]

 Reference Signs List 3 combustion chamber 5 air-fuel ratio measuring unit 7 transmitted light intensity detector 13 air-fuel ratio calculator 20 extinction coefficient detector 22 extinction coefficient corrector

Claims (1)

[Claims] 1. An air-fuel ratio measurement unit provided in a combustion chamber projects light having a wavelength that is selectively absorbed by a fuel vapor from a light-emitting side to a light-receiving side to emit a mixture of fuel vapor and air in the combustion chamber. An internal combustion engine equipped with a transmitted light intensity detection device for detecting the intensity of transmitted light, and an air-fuel ratio calculation device for obtaining an air-fuel ratio before ignition of a combustion chamber based on an output of the transmitted light intensity detection device, an absorption coefficient of fuel, and the like. In the air-fuel ratio detector, the extinction coefficient detector that detects the extinction coefficient of the fuel used in the internal combustion engine, and the extinction coefficient used in the air-fuel ratio calculator, the extinction coefficient newly detected by the extinction coefficient detector An air-fuel ratio detection device for an internal combustion engine, comprising an absorption coefficient correction device for replacing the same or almost the same absorption coefficient.