JP3368687B2 - Air-fuel ratio detection device for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio detecting device for an internal combustion engine, and more particularly to a device for directly detecting the air-fuel ratio of an engine intake air-fuel mixture from the air-fuel mixture in a combustion chamber.

[0002]

2. Description of the Related Art Conventionally, there is known a device for measuring an air-fuel ratio (A / F) of an engine intake air-fuel mixture by detecting combustion light in a combustion chamber. For example, JP-A 1-247
In the air-fuel ratio detection device disclosed in Japanese Patent No. 740, combustion light is taken out by an optical fiber embedded in a spark plug,
The air-fuel ratio is detected by photoelectrically converting the extracted combustion light.

[0003]

However, in the structure for extracting the combustion light by the optical fiber as disclosed in the above-mentioned Japanese Patent Laid-Open No. 1-247740, the emission is mixed with the light emission in the region where the air-fuel ratio is different or the distance is different. Therefore, for example, even if it is desired to accurately obtain the air-fuel ratio in the vicinity of the spark plug, which is a determinant factor of the ignition limit, there is a problem that the light emission in the region away from the spark plug has an influence and thus the highly accurate air-fuel ratio cannot be detected. there were.

Further, in the air-fuel ratio detection based on the combustion light, the air-fuel ratio before ignition cannot be detected, and the air-fuel ratio near the ignition plug at the ignition timing cannot be controlled accurately. . The present invention has been made in view of the above problems, and an object of the present invention is to provide an air-fuel ratio detection device that can stably and accurately detect the air-fuel ratio near the spark plug before ignition for a long period of time.

[0005]

Therefore, in the air-fuel ratio detecting device for an internal combustion engine according to the invention of claim 1, a pair of optical elements are arranged opposite to each other with a predetermined gap in the combustion chamber of the internal combustion engine, and the two light sources are: Two types of light, light absorbed by fuel and light not absorbed by fuel, are projected from one of the pair of optical elements toward the other. Then, the transmitted light intensity detecting means detects the intensity of each of the two types of light projected between the pair of optical elements.

On the other hand, the in-cylinder pressure detecting means detects the in-cylinder pressure of the engine, and the air-fuel ratio calculating means detects the in-cylinder pressure in the in-cylinder pressure detecting means and the above-mentioned 2 detected in the transmitted light intensity detecting means.
The air-fuel ratio of the engine intake air-fuel mixture is calculated based on the intensity of each kind of light. In the air-fuel ratio detection device for an internal combustion engine according to the invention of claim 2, a pair of optical elements are arranged to face each other in a combustion chamber of the internal combustion engine with a predetermined gap, and the two light sources absorb the light absorbed by the fuel and the light absorbed by the fuel. Two types of light, that is, the un-reflected light, are projected from one of the pair of optical elements toward the other. Then, the transmitted light intensity detecting means detects the intensity of each of the two types of light projected between the pair of optical elements.

Here, the light intensity adjusting means absorbs the light absorbed by the fuel projected between the pair of optical elements based on the intensity of the light not absorbed by the fuel detected by the transmitted light intensity detecting means. Adjust the strength of. On the other hand, the in-cylinder pressure of the engine is detected by the in-cylinder pressure detecting means, and the air-fuel ratio calculating means detects the in-cylinder pressure detected by the in-cylinder pressure detecting means and the light absorbed by the fuel detected by the transmitted light intensity detecting means. The air-fuel ratio of the engine intake air-fuel mixture is calculated based on

In the air-fuel ratio detecting device for an internal combustion engine according to the third aspect of the present invention, the pair of optical elements are integrally provided on the ignition plug of the engine. In the air-fuel ratio detecting device for an internal combustion engine according to the invention of claim 4, the two light sources are arranged so as to project light from mutually different sides in the pair of optical elements, respectively. Each of the two types of light is transmitted through the reflection member that transmits the light and reflects the other, is projected between the pair of optical elements, and then is projected again between the pair of optical elements. The light is reflected by the reflecting member that reflects the light and transmits the other light, and the light returning to the light source side by the reflection is guided to the respective transmitted light intensity detecting means by the half mirror.

[0009]

According to the air-fuel ratio detecting device for an internal combustion engine according to the first aspect of the present invention, the light having a property of being absorbed by the fuel and the light having a property of not being absorbed by the fuel are respectively arranged in the combustion chamber so as to face each other. Projected between optical elements. That is, 2
The light of a kind temporarily passes through the combustion chamber and travels, and at this time, the light absorbed by the fuel is attenuated by the fuel (fuel concentration) existing between the optical elements. The light that is not absorbed by the fuel passes through the combustion chamber without being attenuated by the fuel.

However, both of the two types of light are attenuated by dirt on the optical element, and the attenuation level (dirt degree) can be known by the degree of attenuation of light not absorbed by the fuel. The light absorbed by the fuel is attenuated by being affected by both the fuel and the dirt, but the attenuation due to the dirt can be known by the degree of attenuation of the light not absorbed by the fuel. From the attenuation of the absorbed light, it is possible to identify only those due to fuel.

On the other hand, the absorption of light by the fuel changes according to the air-fuel ratio of the engine intake air-fuel mixture and also changes according to the change of the in-cylinder pressure in the compression stroke (the degree of compression of the air-fuel mixture). Therefore, based on the light intensities after passing through the two types of combustion chambers, the attenuation due to dirt is eliminated and only the light attenuation due to fuel is extracted, and the air-fuel ratio is specified by the light absorption by the fuel and the in-cylinder pressure. To do.

In the air-fuel ratio detecting device for an internal combustion engine according to the second aspect of the present invention, as described above, the attenuation of light due to contamination can be known from the attenuation of light that is not absorbed by the fuel. The projection intensity of light was increased by the amount of the dirt, and the light intensity after passing through the combustion chamber was set to the same level as when there was no dirt for the same air-fuel ratio and in-cylinder pressure.

In the air-fuel ratio detecting apparatus for an internal combustion engine according to the third aspect of the present invention, by providing the pair of optical elements integrally with the spark plug, light is transmitted through the combustion chamber space near the spark plug. At the same time, the component structure is simplified. Claim 4
In the air-fuel ratio detection device for an internal combustion engine according to the invention, the light that has once passed through the combustion chamber space between the optical elements is reflected by using a reflecting member and again passed through the combustion chamber space between the optical elements, The light returned to the light source side is guided to the transmitted light intensity detecting means by a half mirror, and further, in order to enable simultaneous detection by making the paths of such light into mutually opposite directions with two kinds of light, the reflection As the members, two reflecting members are used, which have the property of reflecting one light and transmitting the other, and the transmissive / reflective properties are mutually reversed.

[0014]

EXAMPLES Examples of the present invention will be described below. In FIG. 1 showing the system configuration of the present embodiment, a fuel injection valve 3 is provided in an intake port 2 of an internal combustion engine 1, and the fuel injection is performed with respect to air sucked through an air cleaner and a throttle valve (not shown). Fuel is intermittently injected and supplied from the valve 3 to form an air-fuel mixture.

Then, the air-fuel mixture is sucked into the combustion chamber 5 through the intake valve 4 and 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, a catalyst, and a muffler (not shown). Here, an in-cylinder pressure sensor (in-cylinder pressure detection means) 7 for detecting the pressure (in-cylinder pressure) in the combustion chamber 5 is provided, and the cylinder head 8 forming the combustion chamber 5 is penetrated to the spark plug 6 A cylindrical optical element 9 forming an air-fuel ratio detecting device is fitted and held in a mounting hole provided in the vicinity.

As shown in FIGS. 2 (a), 2 (b) and 2 (c), a pair of optical elements (triangular prisms) 10 are provided at the tip of the cylindrical optical element 9 facing the combustion chamber 5. 11 are provided integrally. 2A 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 so as 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 proceed toward 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 ° reflection surface of one of the optical elements 10 and 11 and is incident on the other optical element 10 and 11, while the optical element is reflected by the 45 ° reflection surface of the other optical element 10 and 11. The light beam is bent at a right angle toward the base end side of 9.

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

Although quartz, sapphire or the like is used as a material for the optical elements 9, 10 and 11, sapphire is preferably used in consideration of heat resistance and pressure resistance. Also,
The optical elements 9, 10 and 11 do not have to be formed as a single body, and when polishing of the optical surface is required, for example, according to the division surface shown by the dotted line in FIG. Alternatively, the structure may be a three-part configuration, and the components may be joined after polishing.

In this embodiment, two light sources 12 and 18 are projected to project two kinds of light beams on the optical elements 10 and 11.
Is provided. The light source 12 emits infrared laser light having a wavelength ν1 (for example, wavelength 3.39 μm) absorbed by gasoline fuel, and the light source 18 emits visible laser light having a wavelength ν2 (for example, 632.8 nm) not absorbed by gasoline fuel. .

The laser beam emitted from the light source 12 is bent in a direction parallel to the axis of the optical element 9 toward the optical element 10 by an optical element 13 composed of a mirror, a prism or the like, with respect to the base end surface of the optical element 9. Incident at a right angle. In the base end face of the optical element 9, a wavelength ν is present in a portion through which incident light to the optical element 10 or reflected light from the optical element 10 passes.
An optical film 16 (reflection member) that transmits light of wavelength 1 and reflects light of wavelength ν2 is provided, and the laser beam of wavelength ν1 emitted from the light source 12 passes through the optical film 16 and passes through the optical element 10 Proceed toward.

Then, the light reflected by the 45 ° reflection surface of the optical element 10 and passing through the combustion chamber space to enter the optical element 11 arranged oppositely, the light reflected by the 45 ° reflection surface of the optical element 11 is Although the light travels toward the base end face of the optical element 9, the base end face of the optical element 9 transmits the light of the wavelength ν2 to the portion where the incident light to the optical element 11 or the reflected light from the optical element 11 passes. An optical film 17 (reflection member) that reflects light of wavelength ν1 is provided.

Therefore, the laser beam having the wavelength ν1 reflected by the optical element 11 is reflected by the optical film 17 and is again reflected by the optical element.
The light beam enters the optical element 11 and is reflected by the optical element 11 and the optical element 10. The optical path is returned to the light source 12 side and travels through the optical film 16. The laser beam having the wavelength ν1 that has returned through the optical film 16 is reflected by the half mirror 20a provided between the optical element 13 and the light source 12, enters the photoelectric conversion element 14, and the transmitted light thereof. The intensity is detected by the photoelectric conversion element 14.

The laser beam of wavelength ν1 from the light source 12 passes through the half mirror 20a and reaches the optical element 13. On the other hand, the light source 18 is arranged so that the laser beam having the wavelength ν2 is first incident on the optical element 11 in contrast to the light source 12, and the laser beam having the wavelength ν2 that passes through the optical film 17 is Optical film 16 due to reflection of elements 11 and 10
The half mirror provided between the light source 18 and the optical element 13 after passing through the optical film 17 again after following the optical path that is reflected here and returns to the light source 18 side by the reflection of the optical elements 10 and 11 again. The light is reflected by 20b and enters the photoelectric conversion element 19, and the intensity of the transmitted light is detected by the photoelectric conversion element 19.

In FIG. 1, 15 is the optical element 9 described above.
Is a holder for holding. With this configuration, the laser light of wavelength ν1 absorbed by the gasoline fuel and the laser light of wavelength ν2 not absorbed by the gasoline fuel are both emitted from the light source, and then pass through the optical elements 9, 10, 11 and the combustion chamber space. After passing through, the transmitted light intensity is detected.

The output of the photoelectric conversion elements 14 and 19 (transmitted light intensity detecting means) and the detection signal from the in-cylinder pressure sensor 7 are control units including a microcomputer for controlling fuel injection by the fuel injection valve 3. Entered in 35. The control unit 35 detects the air-fuel ratio of the engine intake air-fuel mixture based on these detection signals, and controls the fuel injection based on the detected air-fuel ratio.

Here, the principle of air-fuel ratio detection in this embodiment will be briefly described. Gasoline fuel used in the engine 1 generally has a property of selectively absorbing infrared light,
In the air-fuel mixture, the absorption amount increases substantially in proportion to the gasoline concentration in the air-fuel mixture. That is, the incident light intensity is I
_{When O 2} , the gasoline concentration are C and the absorption coefficient is K, the absorption amount I can be expressed as I = I _o exp ^-KC .

Therefore, if it is possible to irradiate the air-fuel mixture with infrared light of a predetermined intensity (laser light of wavelength ν1) and detect how much the infrared light is absorbed by the gasoline, the concentration of gasoline in the air-fuel mixture, in other words, Then, the air-fuel ratio of the air-fuel mixture can be detected. Here, in the present embodiment, the pair of optical elements 10 and 11 are arranged so as to face each other with a space in the combustion chamber 5 as a gap, and the laser light having the wavelength ν1 passes through the gap, and finally the photoelectric conversion element 14 is formed. Since the laser beam having the wavelength ν1 is absorbed by an amount commensurate with the gasoline concentration in the air-fuel mixture existing in the gap, the laser beam attenuated by the absorption enters the photoelectric conversion element 14. Become.

Further, the fact that the absorption amount of the laser light (infrared light) is proportional to the gasoline concentration means that the absorption amount changes due to the pressure (cylinder pressure) change in the combustion chamber even in the same air-fuel ratio state. become. Therefore, the calibration characteristic based on the in-cylinder pressure is measured in advance (see FIG. 3), and the calculation characteristic of the air-fuel ratio using the output of the photoelectric conversion element 14 and the in-cylinder pressure detected by the in-cylinder pressure sensor 7 as parameters ( By previously setting the air-fuel ratio calculation means) in the control unit 35, it is possible to calculate the local air-fuel ratio in the combustion chamber 5 from the intake stroke in which the air-fuel mixture is sucked to the ignition timing ( (See FIG. 4).

The air-fuel ratio (local air-fuel ratio near the spark plug 6) detected as described above is used as control information for the injection control (injection amount control, injection timing control) by the control unit 35. The air-fuel ratio in the vicinity of the spark plug at the ignition timing will determine the ignition limit, and is an important factor especially in a lean-burn engine in which the ignitability deteriorates. If the air-fuel ratio can be detected, it becomes possible to control the air-fuel ratio in the vicinity of the spark plug with high accuracy and stably obtain good ignitability.

Further, the transmitted light intensity detected by the photoelectric conversion element 14 is affected only by the air-fuel ratio state in the gap between the pair of optical elements 10, 11 and is not affected by the air-fuel ratio state in other regions of the combustion chamber. Therefore, the local air-fuel ratio can be detected with high accuracy. As the fuel injection control using the detection result of the air-fuel ratio, the injection amount is feedback-controlled to match the detected air-fuel ratio with the target air-fuel ratio, and the rich peak timing of air-fuel ratio fluctuation overlaps with the ignition timing. By controlling the injection timing by the injection valve as described above, the air-fuel ratio near the spark plug can be controlled to a desired state.

By the way, when the optical elements 10 and 11 for guiding the laser light are arranged so as to face the inside of the combustion chamber 5 as described above, stains due to combustion adhere to the optical elements 10 and 11, and the amount of the stains is increased. There is a possibility that the absorption of the laser light (infrared light) by the gasoline fuel cannot be accurately detected by attenuating the laser light. Therefore, in the present embodiment, as described above, similar to the laser light having the wavelength ν1 absorbed by the fuel, the laser light having the wavelength ν2 that is not absorbed by the fuel is projected between the optical elements 10 and 11, and the light caused by the contamination is emitted. Is determined from the attenuation of the laser beam having the wavelength ν2.

That is, the laser light having the wavelength ν1 is affected by both fuel and dirt to be attenuated, but the laser light having the wavelength ν2 is affected by only dirt and is attenuated. Even if there is, it can be considered that they are almost the same. Therefore, based on the attenuation result of the laser light of wavelength ν2, the influence of dirt contained in the attenuation of the laser light of wavelength ν1 is eliminated, and the attenuation by fuel is reduced. You can only ask.

Here, the function of the control unit 35 (air-fuel ratio calculating means) for detecting the air-fuel ratio (gasoline concentration) while correcting the above-mentioned dirt will be described with reference to the flowchart of FIG. In the flowchart of FIG. 5, first, in S1, the light intensity An detected by the photoelectric conversion element 19 of the laser light having the wavelength ν2, which indicates the attenuation level of the laser light due to the dirt, is read.

In the next S2, the wavelength ν1 absorbed by the fuel
The light intensity Bn of the laser light detected by the photoelectric conversion element 14 is read. Then, in S3, the light intensity B for air-fuel ratio measurement is measured.
Divide n by the light intensity An to correct the stain,
The calculation result is set to I as the light intensity with the dirt amount corrected.

In S4, the gasoline concentration C (air-fuel ratio) is calculated based on the light intensity I after the stain correction and the in-cylinder pressure detected by the in-cylinder pressure sensor 7 (see FIG. 3). S
At 5, the n indicating the data number of the air-fuel ratio calculated within the air-fuel ratio calculation period is increased by 1, and at next S6, whether or not it is within the actual measurement period of the air-fuel ratio (for example, a predetermined section before the ignition timing). To determine. Then, if it is not in the actual measurement section, the data number is reset in S7. If it is in the actual measurement section, the flow returns to S1 without performing the reset, and the air-fuel ratio calculation is repeated while performing the dirt correction, and the calculation result is obtained. It is stored in time series (see FIG. 6).

The light intensity A influenced only by the amount of dirt
If n has fallen below a predetermined value, it is judged that the desired transmitted light intensity detection is impossible, and it is preferable to shift to a predetermined fail-safe mode (for example, stop of air-fuel ratio detection). In the above-described embodiment, the light intensity (attenuation level) excluding the influence of dirt is detected based on the detected intensity of the laser beam having the wavelength ν1 absorbed by the fuel and the detected intensity of the laser beam having the wavelength ν2 not absorbed by the fuel. However, if the incident intensity of the laser beam having the wavelength ν1 to the optical element 9 is increased by the attenuation amount due to the dirt, the transmitted light intensity apparently influenced only by the air-fuel ratio is the same as when there is no dirt. Will be detected.

Specifically, since attenuation of light due to dirt is required from attenuation of laser light of wavelength ν2, the intensity of laser light of wavelength ν1 incident on the optical elements 9, 10 and 11 should be increased by this amount. . Adjust the intensity of the laser light in advance by the light source 12
The emission level in the intensity adjusting filter (light intensity adjusting means) for attenuating the intensity of the laser beam having the wavelength ν1 emitted from the light source 12 is set to a high value, and the attenuation level in the intensity adjusting filter corresponds to the amount of attenuation due to the dirt. Control, or the emission intensity itself of the light source 12 is controlled to increase corresponding to the amount of attenuation due to dirt (light intensity adjusting means).

In the above embodiment, the optical element 9 including the pair of optical elements 10 and 11 is arranged near the spark plug 6, but the air-fuel ratio of the electrode atmosphere of the spark plug 6 is controlled. In order to increase the ignition limit, the spark plug 6 (electrode part)
It is desirable to detect the air-fuel ratio at a position as close as possible,
Further, considering the reduction of the number of parts, the assemblability, and the space efficiency in the cylinder head that constitutes the combustion chamber,
It is preferable that the spark plug 6 and the pair of optical elements 10 and 11 are integrally provided.

An embodiment in which the pair of optical elements 10 and 11 are integrally provided on the spark plug 6 will be described with reference to FIGS. 7 to 10, the holder 21 is mounted on the cylinder head by the mounting screw 22, and the holder 21 includes a terminal 23a and a center shaft 23.
b, a central electrode 23c and a ground electrode 23d
Are held offset from the axis of the holder 21.

The holder 21 includes the spark plug body.
The pair of optical elements in the above embodiment is provided in a vacant space portion generated by offsetting and holding 23.
Two cylindrical sapphire rods 24 and 25 corresponding to 10 and 11
Are fixed in parallel with each other with a predetermined interval so as to penetrate the holder 21 in the axial direction. The two sapphire rods 24, 25
As shown in FIG. 10, the tip portion of each has an optical surface cut at 45 °, and by making the optical surfaces face each other, one sapphire rod 24
The laser light from the laser source that has passed through (25) is
The light is reflected by the optical surface of 45 °, is emitted into the space inside the combustion chamber 5, and then is incident on the other sapphire rod 25 (24).

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 into two surfaces by the dotted lines in FIG. It is preferable that the components are configured and integrated after welding by welding or the like. Further, the diameters and positions of the sapphire rods 24 and 25 are preferably set to large values of D ₁ , D ₂ and θ shown in FIG. 9 as long as the diameter of the mounting screw 22 of the holder 21 allows. This is because the thicker the rod, the easier it is to process and assemble, and the larger the reflecting surface can be made.Also, by increasing the distance between the rods, the difference in gasoline concentration can be clearly detected as the difference in the laser light attenuation level. You can do it.

In the structure shown in FIGS. 7 to 10, the two sapphire rods 24, 25 are formed to have the same diameter from the base end side to the tip side having the reflecting surface, and are fixed to the holder 21. However, the mounting method is not limited to this. Further, the sapphire rods 24 and 25 need to face each other with a predetermined gap on the distal end side, but they do not have to be separate bodies on the proximal end side and may be integrated.

Further, in the above embodiment, the sapphire rod
The optical path of the laser light that moves between the rods on the tip side of 24, 25 is configured to pass near the spark gap of the spark plug,
Further, in order to detect the air-fuel ratio that influences the ignitability of the spark plug with high accuracy, the optical path may cross the spark gap so that the local air-fuel ratio near the spark gap can be detected.

11 and 12 show sapphire rods 24 and 25.
However, the laser beam reflected by the 45 ° optical surface on the tip side of the sapphire rod 24 (25) is integrally provided so as to project to the tip of the spark plug with the center electrode 23c of the spark plug interposed therebetween. The light enters the sapphire rod 25 (24) side through the spark gap between the center electrode 23c and the ground electrode 23d. With this configuration, the air-fuel ratio that affects the ignitability of the spark plug can be detected more accurately, and highly accurate air-fuel ratio control is possible without being affected by the air-fuel ratio variation in the combustion chamber 5.

The optical elements 10 and 11 (sapphire rod 2
However, the configuration in which (4, 25) is integrally provided with the spark plug 6 is not limited to the above. However, in the case of detecting the local air-fuel ratio in the combustion chamber 5, the air-fuel ratio of the spark gap portion of the spark plug 6 is detected, and the fuel injection is controlled based on the detection result so as to obtain the desired air-fuel ratio. So the figure is
As shown in FIGS. 11 and 12, it is preferable that optical elements 10 and 11 are arranged on both sides of the spark gap of the spark plug 6 so that the optical path in the combustion chamber 5 crosses the spark gap.

Further, since the optical elements 9, 10 and 11 are arranged facing each other in the combustion chamber, the optical elements 9, 10, 11 are arranged.
Also, the optical films 16 and 17 become hot, and the optical films 16 and 17 may be damaged by heat. Therefore, it is preferable that the periphery of the optical element 9 is covered with a water jacket to be cooled by cooling water so as to prevent damage due to heat.

[0047]

As described above, according to the air-fuel ratio detecting apparatus for an internal combustion engine according to the invention of claim 1, a pair of light of a property absorbed by fuel and light of a property not absorbed by fuel are provided. By transmitting the intensity of the transmitted light through the optical element by detecting the intensity of the transmitted light through the optical element, it is possible to eliminate the influence of dirt on the optical element and accurately detect the light attenuation due to the fuel. There is an effect that the local air-fuel ratio can be detected with high accuracy.

According to the air-fuel ratio detecting apparatus for an internal combustion engine according to the second aspect of the present invention, the projection intensity of the light absorbed by the fuel on the optical element is adjusted according to the influence of the dirt on the optical element. There is an effect that the air-fuel ratio can be obtained from the transmitted light intensity of the light absorbed by the fuel regardless of the presence or absence of dirt. According to the air-fuel ratio detection device for an internal combustion engine of the invention of claim 3, the optical element is integrally provided on the spark plug, so that the structure is simplified and the air-fuel ratio at a position closer to the spark plug is provided. The effect is that detection can be performed.

According to the air-fuel ratio detecting apparatus for an internal combustion engine of the fourth aspect of the present invention, the transmitted light intensity of the two types of light can be detected easily and simply because the reflection member selectively reflects the two types of light. The effect is that they can be done at the same time.

[Brief description of drawings]

FIG. 1 is a system schematic diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an optical element according to the same example.

FIG. 3 is a diagram showing an air-fuel ratio corresponding to transmitted light intensity and in-cylinder pressure.

FIG. 4 is a diagram showing changes in transmitted light intensity and in-cylinder pressure according to a crank angle.

FIG. 5 is a flow chart showing a state of air-fuel ratio calculation accompanied by dirt correction.

FIG. 6 is a diagram showing characteristics of stain correction by light having a wavelength that is not absorbed by fuel.

FIG. 7 is a side view showing an example of a spark plug in which an optical element is integrated.

8 is a top view of the spark plug shown in FIG. 7. FIG.

9 is a bottom view of the spark plug shown in FIG. 7. FIG.

10 is an enlarged view of a tip portion of the optical element shown in FIG. 7.

FIG. 11 is a side view showing an embodiment in which a spark gap of an ignition plug is used as an optical path.

FIG. 12 is a bottom view of the spark plug shown in FIG. 11.

[Explanation of symbols]

1 Internal combustion engine 2 intake ports 3 Fuel injection valve 4 intake valve 5 Combustion chamber 6 spark plug 7 Cylinder pressure sensor 8 cylinder head 9,10,11,13 Optical element 12, 18 Laser source (light source) 14, 19 Photoelectric conversion element (transmitted light intensity detection means) 16, 17 Optical film (reflection member) 20a, 20b Half mirror 21 holder 23 Spark plug body 23c Center electrode 23d Ground electrode 24, 25 sapphire rod 35 Control unit

─────────────────────────────────────────────────── --- Continuation of front page (56) Reference JP-A-6-307953 (JP, A) JP-A-60-188815 (JP, A) JP-A-6-288283 (JP, A) JP-A-1- 247740 (JP, A) Actual development Sho 60-127523 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02D 45/00 F02P 13/00

Claims (4)

(57) [Claims] 1. A pair of optical elements disposed opposite to each other in a combustion chamber of an internal combustion engine with a predetermined gap, and two types of light, light absorbed by fuel and light not absorbed by fuel, respectively, of the pair of optical elements. Two light sources for projecting from one to the other, two transmitted light intensity detecting means for detecting respective intensities of the two types of light projected between the pair of optical elements, and an in-cylinder pressure of an engine are detected. The in-cylinder pressure detection means, the in-cylinder pressure detected by the in-cylinder pressure detection means, and the air-fuel ratio of the engine intake air-fuel mixture are calculated based on the intensities of the two types of light detected by the transmitted light intensity detection means. An air-fuel ratio detecting device for an internal combustion engine, comprising: 2. A pair of optical elements, which are opposed to each other with a predetermined gap in a combustion chamber of an internal combustion engine, and two kinds of light, light absorbed by fuel and light not absorbed by fuel, respectively, of the pair of optical elements. The two light sources for projecting from one to the other, two transmitted light intensity detecting means for detecting the intensity of each of the two types of light projected between the pair of optical elements, and the transmitted light intensity detecting means. Light intensity adjusting means for adjusting the intensity of the light absorbed by the fuel projected between the pair of optical elements based on the detected intensity of the light not absorbed by the fuel, and a cylinder for detecting the cylinder internal pressure of the engine. The internal pressure detection means, the in-cylinder pressure detected by the in-cylinder pressure detection means, and the air-fuel ratio of the engine intake air-fuel mixture are calculated based on the intensity of the light absorbed by the fuel detected by the transmitted light intensity detection means. Air-fuel ratio calculation Air-fuel ratio detecting apparatus for an internal combustion engine, characterized in that it is configured to include a stage, a. 3. The air-fuel ratio detecting device for an internal combustion engine according to claim 1, wherein the pair of optical elements are integrally provided on an ignition plug of the engine. 4. The two light sources are respectively arranged to project light from mutually different sides in the pair of optical elements, while two kinds of light from the two light sources respectively emit the light. After being transmitted through a reflection member that transmits and reflects the other, the reflection member that reflects the light and transmits the other so as to be projected again between the pair of optical elements after being projected between the pair of optical elements. The light reflected by the light source and returned to the light source side by the reflection is guided to each transmitted light intensity detecting means by a half mirror.
An air-fuel ratio detection device for an internal combustion engine according to any one of items 1 to 3.