JPH11229949A - Fuel concentration detector for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect fuel concentration (an air-fuel ratio) inside a combustion chamber over a wide range from a low concentration to a high concentration by means of a simple structure. SOLUTION: When an attenuation ratio of an attenuator (optical attenuator) 19 is variably controlled according to gasoline density, which is replaced by crank angle position, between optical elements 10, 11, light intensity of light incident on between the optical element 10, 11 is variably controlled in compliance with the gasoline density between the optical elements 10, 11. In this way, such transmittance (a predetermined S/N ratio) as allows highly precise fuel concentration detection in spite of a change of the gasoline density between the optical element 10, 11 because of a change in space volume of the whole combustion chamber on the piston upper side, for example, is accomplished in detection of the gasoline density between the optical elements 10, 11, so that the gasoline density between the optical elements 10, 11 can be detected with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel concentration (air-fuel ratio) detecting device for an internal combustion engine, and more specifically, to directly detecting the fuel concentration (air-fuel ratio) of an engine intake air-fuel mixture from an air-fuel mixture in a combustion chamber. Devices that can be used.

[0002]

2. Description of the Related Art In an air-fuel ratio detecting apparatus disclosed in, for example, JP-A-8-74651 and JP-A-8-93542, light having a wavelength easily absorbed by fuel is directed to a combustion chamber of an internal combustion engine. By projecting the light between a pair of optical elements arranged opposite to each other and detecting the transmitted light intensity, the fuel concentration and hence the air-fuel ratio are detected (see FIG. 15).

[0003]

However, the conventional apparatus cannot accurately detect the fuel concentration and the air-fuel ratio over a wide range from a low concentration to a high concentration. That is, the principle of detecting the fuel concentration based on the transmitted light intensity is as follows:
It is as follows.

A fuel concentration detecting section (measuring section) A shown in FIG.
The intensity of transmitted light when there is no light-absorbing substance {fuel (HC)} is Io, and the intensity of light dispersed in front of the detection unit A is Im.
(Output monitor), the transmitted light intensity when there is a light absorbing substance is I
And the logarithm of I / Io [ln (I / I
o)] is the transmittance, the relationship between the transmittance and the concentration (molecular density) is the relationship of the following Lambert beer equation.

Ln (I / Io) =-εLC where ε is the extinction coefficient, L is the optical path length (see FIG. 15), and C is the concentration (molecular density) of the detected gas. From this equation, if the extinction coefficient is known, the concentration (molecular density) can be obtained from the transmittance.

The extinction coefficient can be determined in advance by experiments or the like. In other words, a gas with a known concentration is created, and for example, infrared light (light having a wavelength easily absorbed by fuel molecules) is incident on the gas, and the value of the extinction coefficient is obtained from the concentration and the obtained transmittance value. Can be sought. By the way, since the output of the light source may fluctuate for some reason, in FIG. 15, the spectral intensity Im is monitored,
By correcting the transmitted light intensity I with Im, the transmitted light intensity fluctuation due to the output fluctuation of the light source is corrected so that the density can be measured correctly.

However, in an internal combustion engine, even if the air-fuel mixture having a predetermined air-fuel ratio (fuel concentration) is sucked, the volume of the entire combustion chamber space (cylinder) on the upper side of the piston changes every moment, and the internal combustion chamber (cylinder) changes. Changes the fuel density of
For example, when the piston is at the bottom dead center (when the volume of the entire combustion chamber space above the piston is the maximum), the density of the fuel molecules in the combustion chamber decreases, and I / Io approaches 1 so that a predetermined value is obtained. There is a possibility that the SN ratio cannot be obtained. In other words, when the optical path length L is fixed and the incident light intensity is constant as in the conventional apparatus, high-accuracy concentration detection can be performed only near a specific concentration (specific molecular density).

For this reason, in order to be able to perform density detection with high accuracy (while obtaining a predetermined SN ratio) over a wide range from low density (low density) to high density (high density), the detection is performed. It is conceivable to make the optical path length L variable according to the molecular density of the gas (in other words, the total volume of the space in the combustion chamber above the piston at the time of detection) (see the above Lambert beer equation).

That is, a low-concentration gas (in other words,
In order to detect with high accuracy (when the volume of the entire combustion chamber on the upper side of the piston is large), the optical path length L is increased so that a predetermined number of gas molecules can exist between the optical path lengths L, and a predetermined transmittance is obtained. In order to achieve a predetermined S / N ratio and to detect highly concentrated gas with high accuracy (in other words, when the volume of the entire combustion chamber on the upper side of the piston is small), the optical path length L is shortened and the optical path length is reduced. It is conceivable to limit the number of gas molecules to a predetermined number during the length L so as to achieve a predetermined transmittance and a predetermined SN ratio.

However, when the detection unit is small as in the case of an internal combustion engine (for example, when it is around an ignition plug in a combustion chamber).
However, it is physically difficult to make the optical path length L variable, and even if it is possible, in order to achieve a high response while suppressing the optical system error to a predetermined level, it is structurally extremely complicated. It is extremely difficult to employ such a method because it is expensive and expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a simple structure, and accurately detects the fuel concentration in the combustion chamber and the air-fuel ratio over a wide range from low concentration to high concentration. It is an object of the present invention to provide a fuel concentration (air-fuel ratio) detecting device for an internal combustion engine, which is capable of detecting a fuel concentration. That is, in the present invention, the optical path length L is fixed in order to simplify the configuration and the like, but the concentration detection can be performed with high accuracy (while obtaining a predetermined SN ratio) according to the fuel molecule density. In order to achieve this, the light source light (or incident light) intensity is variably controlled in accordance with the fuel molecule density.

When an air-fuel mixture of a predetermined concentration (air-fuel ratio) is sucked in an internal combustion engine, the fuel molecular density is determined by the space volume of the entire combustion chamber above the piston and the crankshaft rotation angle position (hereinafter also referred to as crank angle position). Therefore, the intensity of the light source (or the incident light) can be variably controlled according to the total volume of the combustion chamber above the piston, the crank angle position, or the like as an alternative characteristic of the fuel molecule density.

Japanese Patent Laying-Open No. 6-288871 discloses a technique for performing in-cylinder photographing in accordance with a crank angle. It is nothing more than doing.

[0014]

Therefore, in the fuel concentration detecting device for an internal combustion engine according to the first aspect of the present invention, as shown in FIG. 1, a pair of opposed fuel cells are disposed in a combustion chamber of the internal combustion engine at a predetermined gap. An optical element, a light source that causes light absorbed by fuel to enter from one side of the pair of optical elements to the other, and a transmitted light intensity detecting unit that detects an intensity of light transmitted between the pair of optical elements. A fuel concentration detecting means for detecting a fuel concentration based on the transmitted light intensity detected by the transmitted light intensity detecting means; and a fuel concentration detecting means for detecting a fuel concentration between the pair of optical elements according to a fuel density between the pair of optical elements. Incident light intensity control means for variably controlling the intensity of the light to be emitted.

With this configuration, the intensity of light incident between the pair of optical elements can be variably controlled in accordance with the fuel density between the pair of optical elements. Even if the chamber space volume changes and the fuel density between the pair of optical elements changes, the transmitted light intensity (or transmittance, SN,
Ratio), the fuel concentration between the pair of optical elements (and hence the air-fuel ratio) can be detected.
The detection accuracy of the fuel concentration (air-fuel ratio) can be significantly improved.

In other words, without adopting an extremely difficult configuration such as changing the optical path length L, a simple and highly reliable configuration is employed, and the fuel molecules which change according to the change in the space volume of the entire combustion chamber above the piston. The fuel concentration (air-fuel ratio) can be detected with high accuracy (while obtaining a predetermined SN ratio) by following the density change. In the invention described in claim 2, the incident light intensity control means changes a light attenuation rate between the pair of optical elements and the light source according to a fuel density between the pair of optical elements. A possible light attenuating means is provided, and the light attenuating rate of the light attenuating means is variably controlled according to the fuel density between the pair of optical elements.

According to this configuration, the incident light intensity control means can be realized with a relatively simple configuration.
In the invention according to claim 3, the light attenuating means is configured to include a liquid crystal, and the voltage applied to the liquid crystal is variably controlled according to the fuel density between the pair of optical elements, so that the light is reduced. The decay rate is variably controlled.

With such a configuration, the light attenuation means can be realized with a relatively simple configuration. Claim 4
In the invention described in (1), the light attenuating means includes a mechanical optical element that is moved according to a change in fuel density between the pair of optical elements and that has a different light attenuation rate in the moving direction. Wherein the mechanical optical element is
By controlling the movement according to the fuel density between the pair of optical elements, the light attenuation rate is variably controlled.

With this configuration, a simpler configuration can be used.
The light attenuation means can be realized. In the invention described in claim 5, the incident light intensity control means is configured to variably control the output of the light source according to the fuel density between the pair of optical elements. With such a configuration, the incident light intensity control means can be realized with a relatively simple configuration.

According to a sixth aspect of the present invention, the fuel density between the pair of optical elements is determined at the time of detection by detecting the rotational angle position of the crankshaft, the piston position, the total volume of the combustion chamber above the piston, the pressure in the combustion chamber, Instead, any one of the gas temperatures in the combustion chamber was used. As an alternative to the fuel density between the pair of optical elements, the rotation angle position of the crankshaft, the piston position, the total volume of the combustion chamber above the piston, the pressure in the combustion chamber (in-cylinder pressure), the temperature in the combustion chamber, etc. can be easily used. With such a configuration, the fuel density between the pair of optical elements can be easily detected.

According to a seventh aspect of the present invention, the mechanical optical element is formed so as to be rotated in synchronization with a crankshaft and to have different attenuation rates of light in the direction of rotation. With this configuration, the light attenuating unit can be realized with a simpler configuration.

According to an eighth aspect of the present invention, the mechanical optical element is connected to a crankshaft. With this configuration, the light attenuating unit can be realized with the simplest configuration.

[0023]

According to the fuel concentration detecting device for an internal combustion engine according to the first aspect of the present invention, the intensity of light incident between the pair of optical elements is changed according to the fuel density between the pair of optical elements. Since the variable control can be performed, even if the entire combustion chamber space volume above the piston changes and the fuel density between the pair of optical elements changes, the transmitted light intensity (or transmitted light) that can accurately detect the fuel concentration can be detected. Ratio, SN ratio), the fuel concentration (air-fuel ratio) between the pair of optical elements can be detected, so that the detection accuracy of the fuel concentration (air-fuel ratio) can be significantly improved.

In other words, without employing an extremely difficult configuration such as changing the optical path length, a simple and highly reliable configuration is employed, and the fuel molecular density changes in accordance with the change in the space volume of the entire combustion chamber above the piston. The fuel concentration (air-fuel ratio) can be detected with high accuracy following the change. According to the second aspect of the present invention, the incident light intensity control means can be realized with a relatively simple configuration.

According to the third aspect of the present invention, the light attenuation means can be realized with a relatively simple configuration.
According to the invention described in claim 4, the light attenuating means can be realized with a simpler configuration. According to the invention described in claim 5, the incident light intensity control means can be realized with a relatively simple configuration.

According to the invention described in claim 6, the fuel density between the pair of optical elements can be easily detected with a simple configuration. According to the invention described in claim 7, the light attenuating means can be realized with a simpler configuration. According to the invention described in claim 8, the light attenuating means can be realized with the simplest configuration.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
Description will be given based on the attached drawings. In FIG. 2 showing the system configuration of the first embodiment of the present invention, a fuel injection valve 3 is provided at an intake port 2 of an internal combustion engine 1 and air sucked through an air cleaner and a throttle valve (not shown). The fuel is intermittently injected from the fuel injection valve 3 to form an air-fuel mixture.

Then, the air-fuel mixture is introduced into the combustion chamber 5 through the intake valve 4 and is ignited and burned by spark ignition by the spark plug 6. Exhaust gas from the engine 1 is discharged into the atmosphere via an exhaust valve (not shown), a catalyst, and a muffler. Here, an in-cylinder pressure sensor (in-cylinder pressure detecting means) 7 for detecting the pressure (in-cylinder pressure) in the combustion chamber 5 is provided, and the ignition plug 6 passes through a cylinder head 8 constituting the combustion chamber 5. A cylindrical optical element 9 is inserted into a mounting hole provided in the vicinity.
Is inserted and held.

As shown in FIGS. 3A, 3B, and 3C, a pair of optical elements (triangular prisms) 10 and 11 are provided integrally. FIG. 3A is a top view of the optical element 9,
(B) is a front view and (c) is a bottom view. The pair of optical elements 10 and 11 are arranged to face each other with a predetermined gap therebetween, enter from the base end face side of the optical element 9 serving as a base, and advance toward the inside of the combustion chamber 5 along the axial direction of the optical element 9. The light beam is bent at a right angle by the 45 ° reflecting surface of one optical element 10 and is incident on the other optical element 11, while the other optical element
The configuration is such that the light beam is bent at a right angle toward the base end side of the optical element 9 at the 11 45 ° reflecting surface.

That is, the light beam is projected between the pair of optical elements 10 and 11 so that the optical element 10
When the air-fuel mixture advances toward the optical element 11, the air passes through the gap between them, that is, the space in the combustion chamber. When the air-fuel mixture exists in the combustion chamber 5 from the suction stroke to the ignition, The light beam is transmitted through the air-fuel mixture through the elements 10 and 11.

As the material of the optical elements 9, 10, and 11, quartz, sapphire, or the like is used, but sapphire is preferably used in consideration of heat resistance and pressure resistance. The optical elements 9, 10, and 11 do not need to be formed as an integral body. When the optical surface needs to be polished, for example, a divided surface shown by a dotted line in FIG. , And may be joined after polishing.

The light source 12 emits infrared laser light having a wavelength ν (for example, a wavelength of 3.39 μm) absorbed by gasoline fuel. Then, as shown in FIG. 2, the laser beam emitted from the light source 12 is parallel to the axis of the optical
, And enters the optical element 9 at right angles to the base end face thereof. After that, the optical element is reflected by the 45 ° reflecting surface of the optical element 10 and passes through the combustion chamber space and is opposed to the optical element.
Light incident on 11 and reflected by the 45 ° reflecting surface of the optical element 11 is
A laser beam having a wavelength ν that travels toward the base end face of the optical element 9 passes through an optical fiber 14 and is received by a photodetector (photoelectric conversion element).
The photoelectric conversion element 15 detects the transmitted light intensity.

The laser beam having the wavelength ν from the light source 12 is reflected by the half mirror 16 and is incident on a light receiver (photoelectric conversion element) 17, and the light intensity is detected by the photoelectric conversion element 17. It has become. By the way, in the present embodiment, the crank angle sensor 18 for detecting the rotation angle position of the crankshaft of the engine 1 (or the rotation angle position of the camshaft).
Is provided, and the detection signal is input to a control unit 35 described later.

The outputs of the photodetectors (photoelectric conversion elements) 15 and 17 and the detection signal from the in-cylinder pressure sensor 7 are input to a control unit 35 having a microcomputer for controlling fuel injection by the fuel injection valve 3. Is done. The A / F detection unit in the control unit 35 detects the fuel concentration in the combustion chamber and the air-fuel ratio of the engine intake air-fuel mixture based on these detection signals, and the fuel supply control unit in the control unit 35 performs the detection. The fuel injection is controlled based on the set air-fuel ratio.

Here, the principle of detecting the fuel concentration (air-fuel ratio) in the present embodiment is the same as described above, and will be briefly described below. That is, the gasoline fuel used for the engine 1 is
Generally, it has a property of selectively absorbing infrared light, and in an air-fuel mixture, the amount of absorption increases substantially in proportion to the gasoline concentration in the air-fuel mixture. That is, if the transmitted light intensity is I, the incident light intensity is I _O (known), the gasoline concentration is C, the extinction coefficient is ε (known), and the optical path length is L (known), the transmittance l
n (I / Io) = − εLC (FIG.
15).

Therefore, when the mixture is irradiated with infrared light (laser light having a wavelength ν) of a predetermined intensity I _O and the transmitted light intensity I is detected, the gasoline concentration C in the mixture, in other words, The air-fuel ratio of the air-fuel mixture can be detected. In the present embodiment, the pair of optical elements 10 and 11 are opposed to each other with a space in the combustion chamber 5 as a gap, and a laser beam having a wavelength ν passes through the gap. Since it is configured to be incident, the laser light having the wavelength ν is absorbed by an amount corresponding to the gasoline concentration in the gas mixture present in the gap,
The laser light attenuated by the absorption enters the light receiver (photoelectric conversion element) 15. The photodetector (photoelectric conversion element) 15 functions as the transmitted light intensity detecting means according to the present invention. However, the absorption amount of the laser light (infrared light) depends on the pair of optical elements 10 and 11. Since it is proportional to the density of the fuel molecules existing between them, even if the fuel concentration is the same {air-fuel ratio (air weight / fuel weight)}, if the fuel molecule density in the combustion chamber (between the optical elements 10 and 11) changes, it is absorbed The amount changes, so that the transmission intensity and thus the transmittance ln (I / Io) change.

That is, when the density is low (when the piston is near the bottom dead center and the total volume of the combustion chamber above the piston is large), I / Io is too close to 1; (When the piston is near the top dead center and the total volume of the combustion chamber above the piston is small), I / Io becomes too small, so that the transmittance with high accuracy and the predetermined S
There is a possibility that the gasoline concentration between the optical elements 10 and 11 that changes from moment to moment (gasoline concentration at each crank angle) cannot be detected by the N ratio, which may lead to a decrease in detection accuracy.

For this reason, in the present embodiment, FIGS.
As shown in (appearance system diagram), an attenuator (light attenuator) 19 is interposed between the light source 12 and the half mirror 16. The attenuator 19 uses liquid crystal, and is configured so that the attenuation rate of light passing through the attenuator 19 can be variably controlled by controlling the voltage applied to the liquid crystal (for example, meadow lark, UK). Etc.).

The control unit 35 receives the signal from the crank angle sensor 18 and controls the attenuator driving device 20 in accordance with the crank angle position (and, consequently, the gasoline density between the optical elements 10 and 11). Nineteen attenuation rates can be changed. That is, by changing the incident light intensity according to the gasoline density between the optical elements 10 and 11 (substituted by the crank angle position), it is possible to improve the transmittance with high precision and, hence, the optical signal at a predetermined SN ratio. The gasoline density (and hence the air-fuel ratio) between the elements 10 and 11 can be detected with high accuracy. Here, the attenuator 19, the attenuator driving device 20
These constitute a part of the incident light intensity control means and the light attenuation means according to the present invention.

That is, the control unit 35 in the first embodiment performs control as shown in the flowchart of FIG. As will be described later, the control unit 35 performs software functions as a transmitted light intensity detecting unit, a fuel concentration detecting unit, an incident light intensity controlling unit, and a light attenuating unit according to the present invention.

That is, in step (denoted by S in the figure, the same applies hereinafter) 1, the crank angle position is detected. In addition, even if it is not the crank angle position, the optical element 10,
Piston position, which can be substituted as gasoline density between 11
It can also be used for the total volume of the combustion chamber above the piston, the pressure in the combustion chamber (in-cylinder pressure), and the like.

In step 2, the required transmittance (the transmittance or S for accurate detection) corresponding to the crank angle position is determined.
N ratio) is calculated. In step 3, the attenuator driving device 20 is controlled so as to achieve the control voltage calculated in step 2, and the attenuator is controlled.
In 19, the control voltage calculated in step 2 is applied.

In step 4, the spectral intensity Im after passing through the attenuator 19 is converted into a voltage by the light receiving device (photoelectric conversion element) 17. That is, the transmittance is expressed as ln (I / Im)
= −εLC. However, since it is In (I / Io) in principle, the spectral ratio is adjusted so that Io (transmitted light) and Im (monitor light) are equal. When the output of the light source 12 does not fluctuate or the like, the predetermined incident light intensity Io is used without using the spectral intensity Im after passing through the attenuator 19.
(Set according to the crank angle position) can also be used.

In step 5, the light intensity I after passing through the detecting section (measuring section; between the optical elements 10 and 11) is converted into a voltage by the photodetector (photoelectric conversion element) 15. In step 6, the transmittance is calculated from the spectral voltage obtained in step 4 and the transmitted light voltage of the detection unit (measurement unit) obtained in step 5 from the Lambert beer equation. In step 7, based on the transmittance, the light absorption characteristics of the detection target at the detection unit pressure / temperature {the ratio of the gas having a certain concentration (density) to absorb at a certain temperature / pressure; Calculate the gasoline concentration (and hence the air-fuel ratio).

In step 8, the calculation result of the concentration (or air-fuel ratio) is output in a time series (for example, according to the crank angle position) (for example, to an external display or the fuel control unit). In step 9, it is determined whether or not the measurement has been completed. If YES, the present flow ends, and if NO, the process returns to step 1.

Whether or not the measurement has been completed is determined, for example, by determining whether or not the current crank angle is within a predetermined crank angle range (for example, from the intake stroke to the ignition timing, or from the intake stroke to the end of the expansion stroke). And so on. That is, it can be determined based on whether the fuel density (air-fuel ratio) is within the actual measurement period. As described above, according to the first embodiment, the gasoline density between the optical elements 10 and 11 is controlled by variably controlling the attenuation rate of light passing through the attenuator 19 according to the gasoline density between the optical elements 10 and 11. The intensity of the incident light can be variably controlled in accordance with the conditions of the optical elements 10 and 11 even if the volume of the entire combustion chamber above the piston changes.
Even if the gasoline density changes, the gasoline concentration between the optical elements 10 and 11 (and hence the air-fuel ratio) can be detected with high accuracy with a high transmittance and a predetermined SN ratio. Becomes

In other words, without adopting an extremely difficult configuration such as changing the optical path length L, a simple and highly reliable configuration is employed, and the fuel molecules that change according to the change in the space volume of the entire combustion chamber above the piston. Following the density change (in other words, over a wide range from low density to high density), gasoline concentration (air-fuel ratio) with high accuracy (while obtaining a predetermined SN ratio)
The detection can be performed.

In this embodiment, the crank angle position is used as an alternative characteristic of the gasoline density between the optical elements 10 and 11, but the piston position, the total volume of the combustion chamber above the piston, the pressure in the combustion chamber (in-cylinder pressure) ), The temperature in the combustion chamber can be substituted. The fuel concentration (local air-fuel ratio in the vicinity of the ignition plug 6) detected as described above is used as control information of fuel supply control (fuel injection amount control and fuel injection timing control) by the control unit 35. The fuel concentration (air-fuel ratio) near the ignition plug at the ignition timing determines the ignition limit, and is an important factor particularly in a lean-burn engine in which the ignitability deteriorates. If the fuel concentration (air-fuel ratio) in the vicinity of the ignition plug can be detected, the fuel concentration (air-fuel ratio) in the vicinity of the ignition plug can be controlled with high accuracy, and good ignitability can be stably obtained.

The transmitted light intensity detected by the photoelectric conversion element 15 is affected only by the air-fuel ratio state in the gap between the pair of optical elements 10 and 11, and is not affected by the air-fuel ratio state in other areas of the combustion chamber. Thus, the local air-fuel ratio can be detected with high accuracy. As the fuel supply control using the detection result of the air-fuel ratio, the fuel supply amount is feedback-controlled so that the detected air-fuel ratio matches the target air-fuel ratio. By controlling the injection timings of the fuel injection valves so that they overlap, the air-fuel ratio near the ignition plug can be controlled to a desired state.

Next, a second embodiment of the present invention will be described. FIG. 6 shows a system configuration of the second embodiment. The arrangement of the optical element 9 and the like may be the same as in the first embodiment. Therefore, the system configuration diagram as shown in FIG. 2 including the combustion chamber cross-sectional structure described in the first embodiment is omitted. Further, the same elements as those described in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

That is, in the second embodiment, the fuel concentration (air-fuel ratio) can be detected with high accuracy by following the change in the fuel molecule density that changes according to the change in the volume of the entire combustion chamber above the piston. For this purpose, the following configuration is adopted. That is, in the second embodiment, as shown in FIG. 6, a light source intensity control device 30 is provided, whereby the output (light intensity) of the light source 12 is controlled by the gasoline density between the optical elements 10 and 11 (for example, the crankshaft). (Angle position). Here, the light source intensity control device
30 constitutes a part of the incident light intensity control means according to the present invention.

The control unit 35 according to the second embodiment performs control as shown in the flowchart of FIG. As will be described later, the control unit 35 performs software functions as the transmitted light intensity detection unit, the fuel concentration detection unit, and the incident light intensity control unit according to the present invention. That is, in step 11, the crank angle position is detected.
The piston position, the volume of the entire combustion chamber above the piston, and the pressure in the combustion chamber (in-cylinder pressure) can be substituted for the gasoline density between the optical elements 10 and 11 even if it is not the crank angle position.
Etc. can also be used.

In step 12, the required light intensity (transmittance or S for accurate detection) corresponding to the crank angle position is determined.
N ratio) is calculated. Steps
In 13, the light source intensity control device 30 is controlled so as to achieve the control voltage calculated in Step 12, and the light source 12 is controlled in Step 13.
The control voltage calculated in 12 is applied.

In step 14, the spectral intensity Im is converted into a voltage by the photodetector (photoelectric conversion element) 17. Note that the reason for using the spectral intensity Im is the same as in the first embodiment. In step 15, the detection unit (measurement unit; optical element 10,
11), the light intensity I after transmission through the light receiver (photoelectric conversion element)
Convert to voltage at 15.

In step 16, the transmittance is calculated from the spectral voltage obtained in step 14 and the transmitted light voltage of the detection unit (measurement unit) obtained in step 15 by the Lambert beer equation. In step 17, based on the transmittance, the light absorption characteristics of the detection target at the detection unit pressure / temperature {the ratio of the gas having a certain concentration (density) to absorb at a certain temperature / pressure; Calculate the gasoline concentration (and hence the air-fuel ratio).

In step 18, the calculation result of the concentration (or the air-fuel ratio) is output in a time series (for example, according to the crank angle position) (for example, to an external display or the fuel control unit). In step 19, it is determined whether or not the measurement has been completed. If YES, the flow ends, and if NO, the process returns to step 1.

As described above, according to the second embodiment, the output (light intensity) of the light source 12 is variably controlled in accordance with the gasoline density between the optical elements 10 and 11, so that the optical elements 10 and 11 can be controlled. Since the incident light intensity can be variably controlled according to the gasoline density, even if the gasoline density between the optical elements 10 and 11 changes due to a change in the total volume of the combustion chamber above the piston, accurate transmission can be achieved. It is possible to detect the gasoline concentration between the optical elements 10 and 11 (and hence the air-fuel ratio) with high accuracy by using a predetermined SN ratio.

In other words, without adopting an extremely difficult configuration such as changing the optical path length L, a simple and highly reliable configuration is employed, and the fuel molecules which change in accordance with the change in the volume of the entire combustion chamber above the piston are changed. Following the density change (in other words, over a wide range from low density to high density), gasoline concentration (air-fuel ratio) with high accuracy (while obtaining a predetermined SN ratio)
The detection can be performed.

In the second embodiment, the optical elements 10 and
As a substitute characteristic of the gasoline density between the 11 units, the crank angle position was used, but the piston position, the total volume of the combustion chamber above the piston, the pressure in the combustion chamber (in-cylinder pressure), the temperature in the combustion chamber, etc. is there. In the first and second embodiments, the case where the gasoline concentration (air-fuel ratio) is detected with high accuracy following the change in the fuel molecular density which changes in accordance with the change in the volume of the entire combustion chamber above the piston is mainly described. However, the present invention is also applicable to the case where the fuel concentration (air-fuel ratio) of the air-fuel mixture sucked by the engine is operated at a low concentration or at a high concentration, and in this case, the optical element is used. The incident light intensity is variably controlled according to the gasoline density change between 10 and 11, and according to the concentration of the intake air mixture (this is
The intensity of incident light can be variably controlled according to the change in gasoline density between the optical elements 10 and 11).

Next, a third embodiment of the present invention will be described. FIG. 8 shows a system configuration of the third embodiment. The arrangement of the optical element 9 and the like may be the same as in the first embodiment. Therefore, the system configuration diagram as shown in FIG. 2 including the combustion chamber cross-sectional structure described in the first embodiment is omitted. Further, the same elements as those described in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

That is, in the third embodiment, the fuel concentration (air-fuel ratio) can be detected with high accuracy by following the change in the fuel molecule density that changes according to the change in the volume of the entire combustion chamber above the piston. For this purpose, the following configuration is adopted. That is, in the third embodiment, as shown in FIG. 8, a disk-shaped attenuator 40 which is connected to a crankshaft (or a camshaft; hereinafter, represented by a crankshaft) and rotates synchronously is provided. Through this, the light from the light source 12 is made incident on the optical element 9 so that the intensity of the incident light is variably controlled according to the gasoline density (crank angle position) between the optical elements 10 and 11. The disk-shaped attenuator 40 is a mechanical optical element (such as plastic or glass) and is formed so as to achieve a required transmittance (in other words, a required attenuation rate) according to the crank angle position. (For example, a reflective film or the like having a different transmittance in a gradation manner with respect to the rotation direction is applied or fused).

Here, the attenuator 40 constitutes a part of the incident light intensity control means and the light attenuation means according to the present invention. The control unit 35 according to the third embodiment performs control as shown in the flowchart of FIG. As will be described later, the software function as the transmitted light intensity detecting means and the fuel concentration detecting means according to the present invention is performed by the control unit 35. That is, in step 21, the spectral intensity Im after passing through the attenuator 40 is
The light is converted into a voltage by a light receiver (photoelectric conversion element) 17. That is, the transmittance is calculated as In (I / Im) = − εLC. When the light source 12 does not have an output fluctuation or the like, a predetermined voltage value of the incident light intensity Io (set according to the crank angle position) can be used without using the spectral intensity Im.

In step 22, the light intensity I after passing through the detection unit (measurement unit; between the optical elements 10 and 11) is converted into a voltage by the photodetector (photoelectric conversion element) 15. In step 23, the transmittance is calculated from the spectral voltage obtained in step 21 and the transmitted light voltage of the detection unit (measurement unit) obtained in step 22 by the Lambert beer equation. In step 24, based on the transmittance, the light absorption characteristics of the detection target at the detection unit pressure / temperature {the ratio of the gas having a certain concentration (density) to absorb at a certain temperature / pressure; Calculate the gasoline concentration (and hence the air-fuel ratio).

In step 25, the calculation result of the concentration (or the air-fuel ratio) is output in time series (for example, to an external display or the fuel control unit) (for example, according to the crank angle position). In addition, when outputting at every crank angle position, the crank angle position is separately detected. Steps
At 26, it is determined whether or not the measurement has been completed. If YES, this flow is finished; if NO, the process returns to step 1.

As described above, according to the third embodiment, the attenuator 40 depends on the gasoline density between the optical elements 10 and 11.
Optical element by variably controlling the attenuation rate of light passing through
Since the incident light intensity can be variably controlled according to the gasoline density between 10 and 11, even if the total volume of the combustion chamber above the piston changes and the gasoline density between the optical elements 10 and 11 changes. , The transmittance with high accuracy and the predetermined S
With the N ratio, the gasoline concentration between the optical elements 10 and 11 (and hence the air-fuel ratio) can be detected with high accuracy.

In other words, a simple and highly reliable configuration is employed without employing an extremely difficult configuration such as changing the optical path length L. Following the density change (in other words, over a wide range from low density to high density), gasoline concentration (air-fuel ratio) with high accuracy (while obtaining a predetermined SN ratio)
The detection can be performed.

Moreover, in the present embodiment, the attenuator 19, the attenuator driving device 20, the light source intensity control device and the attenuator 19, which are relatively expensive and require complicated control logic as described in the first and second embodiments. Since the mechanical attenuator 40 is used without using the 30, the maximum simplification of the configuration and simplification of the control logic can be achieved to reduce the operation processing time and the storage capacity. It becomes possible.

Next, a fourth embodiment of the present invention will be described. FIG. 10 shows the system configuration of the fourth embodiment. The arrangement of the optical element 9 and the like may be the same as in the first embodiment. Therefore, the system configuration diagram as shown in FIG. 2 including the combustion chamber cross-sectional structure described in the first embodiment is omitted. Further, the same elements as those described in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

That is, in the fourth embodiment, the fuel concentration (air-fuel ratio) can be detected with high accuracy by following the change in the fuel molecule density which changes in accordance with the change in the volume of the entire combustion chamber above the piston. For this purpose, the following configuration is adopted. That is, in the fourth embodiment, as shown in FIG. 10, a disk-shaped attenuator 50 that is connected to and rotates with a pulse motor 51 that is driven and controlled via a pulse motor driving device 52 is provided. By making the light of the light source 12 incident on the optical element 9 via the attenuator 50, the intensity of the incident light is variably controlled according to the gasoline density (crank angle position) between the optical elements 10 and 11. . The disk-shaped attenuator 50 is, like the attenuator 40 in the third embodiment, required transmission according to the rotational angle position of the pulse motor 51 (and, in turn, the crank angle position or cam angle position of the engine 1). The rate (in other words, the required attenuation rate) is formed.

Here, the attenuator 50, the pulse motor 51, and the pulse motor driving device 52 constitute a part of the incident light intensity control means and the light attenuation means according to the present invention. The control unit 35 according to the fourth embodiment performs control as shown in the flowchart of FIG. As will be described later, the control unit 35 performs software functions as a transmitted light intensity detecting unit, a fuel concentration detecting unit, an incident light intensity controlling unit, and a light attenuating unit according to the present invention.

That is, in step 31, the crank angle position is detected. It is to be noted that the piston position, the total volume of the combustion chamber above the piston, the pressure in the combustion chamber (in-cylinder pressure), and the like, which can be substituted for the gasoline density between the optical elements 10 and 11, can be used instead of the crank angle position.

In step 32, the required attenuation rate (transmittance or S for accurate detection) corresponding to the crank angle position is determined.
The control voltage required to rotate the pulse motor 51 to achieve the N ratio) is calculated. In step 33, the pulse motor driving device 52 is controlled so that the control voltage calculated in step 32 is achieved, and the pulse motor 51
The control voltage calculated in 32 is applied.

In step 34, the spectral intensity Im having passed through the attenuator 50 is converted into a voltage by the light receiving device (photoelectric conversion element) 17. That is, the transmittance is expressed as ln (I / Im) = −
It is calculated as εLC. The light source 12
In the case where there is no output fluctuation or the like, a predetermined voltage value of the incident light intensity Io (set according to the crank angle position) can be used without using the spectral intensity Im.

In step 35, the detecting section (optical elements 10, 11)
Light intensity I after passing through the light receiving device (photoelectric conversion element) 15
To convert to voltage. In step 36, the transmittance is calculated from the spectral voltage obtained in step 34 and the detection unit transmitted light voltage obtained in step 35 from the Lambert beer equation. In step 37, based on the transmittance, the light absorption characteristics of the detection target at the pressure and temperature of the detection portion {the ratio of the gas of a certain concentration (density) absorbing at a certain temperature and pressure; Calculate the gasoline concentration (and hence the air-fuel ratio).

In step 38, the calculation result of the concentration (or the air-fuel ratio) is output in time series (for example, to an external display or the fuel control unit) (for example, according to the crank angle position). In step 39, it is determined whether or not the measurement has been completed. If YES, this flow ends, and if NO, the process returns to step 31.

As described above, according to the fourth embodiment, the attenuator 50 according to the gasoline density between the optical elements 10 and 11.
Optical element by variably controlling the attenuation rate of light passing through
Since the incident light intensity can be variably controlled according to the gasoline density between 10 and 11, even if the total volume of the combustion chamber above the piston changes and the gasoline density between the optical elements 10 and 11 changes. , The transmittance with high accuracy and the predetermined S
With the N ratio, the gasoline concentration between the optical elements 10 and 11 (and hence the air-fuel ratio) can be detected with high accuracy.

In other words, without adopting an extremely difficult configuration such as changing the optical path length L, a simple and highly reliable configuration is employed, and the fuel molecules that change in accordance with the change in the volume of the entire combustion chamber above the piston are changed. Following the density change (in other words, over a wide range from low density to high density), gasoline concentration (air-fuel ratio) with high accuracy (while obtaining a predetermined SN ratio)
The detection can be performed.

Further, in the present embodiment, the attenuator 19, the attenuator driving device 20, the light source intensity control device, and the like which are relatively expensive and require complicated control logic as described in the first and second embodiments are used. Since the mechanical attenuator 50 is used without using the 30, the simplification of the configuration, the simplification of the control logic, and the shortening of the arithmetic processing time and the reduction of the storage capacity can be promoted. Become.

In each of the above embodiments, the configuration has been described in which the fuel concentration is detected by using the transmittance. However, this is achieved by correcting fluctuations in the output (incident light intensity) of the light source 12 to obtain a good fuel concentration. It is for detecting the concentration,
When there is no change in the output (incident light intensity) of the light source 12 or when there is no influence on the detection accuracy, the fuel concentration can be detected only by the transmitted light intensity.

In each of the above embodiments, the ignition plug 6
The optical element 9 having the pair of optical elements 10 and 11 is disposed near the optical element. However, in order to control the air-fuel ratio of the electrode atmosphere of the ignition plug 6 to increase the ignition limit, for example, Stopper 6
(Electrode part) It is desired to detect the air-fuel ratio at a position as close as possible, and in consideration of reduction in the number of parts, assemblability and space efficiency in the cylinder head constituting the combustion chamber, the ignition plug 6 and the pair of Preferably, the optical elements 10 and 11 are provided integrally.

Here, an example in which the pair of optical elements 10 and 11 are provided integrally with the ignition plug 6 will be described with reference to FIGS. 12 to 14, a holder 21 is mounted on a cylinder head by a mounting screw 22. The holder 21 has a terminal 23a, a center shaft 23b,
An ignition plug main body 23 composed of a center electrode 23c and a ground electrode 23d is held offset from the axis of the holder 21.

The holder 21 includes the ignition plug main body.
Two cylindrical sapphire rods 24, which correspond to the pair of optical elements 10, 11 in the above embodiment, are provided in an empty space generated by holding the offset 23.
25 are fixedly penetrated in the axial direction of the holder 21 in parallel at a predetermined interval. The two sapphire rods 24,
As shown in FIGS. 12 and 13, the distal end portion of each of the sapphire rods 24 has an optical surface cut at 45 °, and the optical surfaces are opposed to each other, as in the above-described embodiment. The laser light from the laser source that has passed through is reflected by the 45 ° optical surface, emitted to the space in the combustion chamber 5, and then enters the other sapphire rod 25.

Since the optical surfaces of the sapphire rods 24 and 25 on which the laser light is reflected or transmitted need to be sufficiently polished, for example, the sapphire rods 24 and 25 are divided by a surface shown by a dotted line in FIG. It is good to make it a component structure and to integrate it by welding etc. after polishing. In the configuration shown in FIG. 12, the two sapphire rods 24 and 25 are formed to have the same diameter from the base end side to the distal end side having the reflection surface, and are fixed to the holder 21. The method is not limited.

Further, the sapphire rods 24 and 25 need to face each other with a predetermined gap on the tip side.
The base end does not need to be separate and may be integrated. The optical path of the laser beam moving between the rods at the tip ends of the sapphire rods 24 and 25 may be configured to pass near the spark gap (ignition gap) of the spark plug, but the ignitability of the spark plug is affected. In order to detect the air-fuel ratio with high accuracy, as shown in FIG. 13 and FIG. 14, the optical path crosses the spark gap (ignition gap) so that the local air-fuel ratio near the spark gap can be detected. Can be.

That is, as shown in FIG. 13 and FIG. 14, the laser beam reflected by the 45 ° optical surface on the tip side of the sapphire rod 24 causes a spark gap (ignition gap) between the center electrode 23c and the ground electrode 23d. Through to the sapphire rod 25 side. According to such a configuration, the air-fuel ratio that affects the ignitability of the ignition plug can be more accurately detected, and highly accurate air-fuel ratio control can be performed without being affected by the air-fuel ratio variation in the combustion chamber 5.

In each of the above embodiments, the fuel has been described as gasoline. However, the present invention can be applied to other fuels such as light oil, alcohol, LPG, CNG and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

FIG. 2 is a system configuration diagram (part 1) showing the first embodiment of the present invention.

FIG. 3 is a diagram showing an optical element in the embodiment.

FIG. 4 is a system configuration diagram showing the embodiment (part 2);

FIG. 5 shows a fuel concentration (air-fuel ratio) performed in the embodiment.
9 is a flowchart illustrating a detection (calculation) routine.

FIG. 6 is a system configuration diagram showing a second embodiment of the present invention.

FIG. 7 shows a fuel concentration (air-fuel ratio) performed in the embodiment.
9 is a flowchart illustrating a detection (calculation) routine.

FIG. 8 is a system configuration diagram showing a third embodiment of the present invention.

FIG. 9 shows a fuel concentration (air-fuel ratio) performed in the embodiment.
9 is a flowchart illustrating a detection (calculation) routine.

FIG. 10 is a system configuration diagram showing a fourth embodiment of the present invention.

FIG. 11 shows a fuel concentration (air-fuel ratio) performed in the embodiment.
9 is a flowchart illustrating a detection (calculation) routine.

FIG. 12 is a side view showing an example of an ignition plug in which an optical element is integrated.

FIG. 13 is a side view showing an embodiment in which a spark gap of an ignition plug is used as an optical path.

14 is a bottom view of the ignition plug shown in FIG.

FIG. 15 is a system configuration diagram of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake port 3 Fuel injection valve 4 Intake valve 5 Combustion chamber 6 Spark plug 9, 10, 11 Optical element 12 Laser source (light source) 13, 14 Optical fiber 15 Light receiver (photoelectric conversion element; transmitted light intensity detection means) 16 Half mirror 17 Optical receiver (photoelectric conversion element) 18 Crank angle sensor 19 Attenuator (light attenuating means) 20 Attenuator driving device 30 Light source intensity control device 35 Control unit (CPU) 40, 50 Attenuator (light attenuating means) 51 Pulse motor 52 Pulse motor drive

Claims (8)

[Claims] A pair of optical elements disposed opposite to each other with a predetermined gap in a combustion chamber of an internal combustion engine; a light source for causing light absorbed by fuel to enter from one of the pair of optical elements to the other; Transmitted light intensity detecting means for detecting the intensity of light transmitted between the optical elements, fuel concentration detecting means for detecting a fuel concentration based on the transmitted light intensity detected by the transmitted light intensity detecting means, An incident light intensity control means for variably controlling the intensity of light incident between the pair of optical elements in accordance with the fuel density between the pair of optical elements; Concentration detection device. 2. An optical attenuation device according to claim 1, wherein said incident light intensity control means changes a light attenuation rate between said pair of optical elements and said light source in accordance with a fuel density between said pair of optical elements. 2. The fuel concentration detecting device for an internal combustion engine according to claim 1, wherein means is interposed, and a light attenuation rate of the light attenuating means is variably controlled according to a fuel density between the pair of optical elements. 3. The light attenuating means is configured to include a liquid crystal, and a voltage applied to the liquid crystal is variably controlled according to a fuel density between the pair of optical elements to change a light attenuation rate. 3. The control system according to claim 2, wherein
3. A fuel concentration detecting device for an internal combustion engine according to claim 1. 4. The optical attenuating means includes a mechanical optical element which is moved in accordance with a change in fuel density between the pair of optical elements and which has a different light attenuation rate in a moving direction. 3. The apparatus according to claim 2, wherein the mechanical optical element is configured to move and control the mechanical optical element according to a fuel density between the pair of optical elements, thereby variably controlling a light attenuation rate. Fuel concentration detecting device for an internal combustion engine. 5. The fuel concentration of an internal combustion engine according to claim 1, wherein said incident light intensity control means variably controls an output of said light source according to a fuel density between said pair of optical elements. Detection device. 6. A fuel density between said pair of optical elements, a rotation angle position of a crankshaft, a piston position, a space volume of all combustion chambers above the piston, a pressure in the combustion chamber at the time of detection.
The fuel concentration detecting device for an internal combustion engine according to any one of claims 1 to 5, wherein the temperature is replaced by any one of a gas temperature in a combustion chamber. 7. The internal combustion engine according to claim 4, wherein said mechanical optical element is rotated in synchronization with a crankshaft, and is formed so as to have different attenuation rates of light in the direction of rotation. Fuel concentration detector. 8. The fuel concentration detecting device for an internal combustion engine according to claim 7, wherein said mechanical optical element is connected to a crankshaft.