JP3975838B2 - In-cylinder observation device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for observing a combustion chamber of an internal combustion engine.
[0002]
[Prior art]
Conventionally, there is a spectroscopic analysis method using a Raman spectrum as a method for examining the gas composition when the fuel ignited in the combustion chamber burns.
[0003]
In order to perform the Raman spectroscopic analysis, a visualization window is provided in advance on a part of the wall constituting the combustion chamber, and high-power laser light is irradiated into the combustion chamber from the visualization window. After this laser light hits the substance in the combustion chamber and emits Raman light corresponding to the molecules constituting each substance, the laser light was formed between the electrode gaps of the plugs protruding into the combustion chamber. Incident in the gap.
[0004]
[Problems to be solved by the invention]
In a mode in which laser light enters a gap between electrodes provided on the plug, the gap between the electrodes is narrow, and scattered light due to the laser light is generated near the entrance.
[0005]
The Raman light generated when the laser beam strikes each molecule is weak light. If there is another light source, the light from that light source becomes noise, and the exact excitation position of the wavelength specific to the substance to be measured can be specified. It becomes difficult.
[0006]
Not only the Raman spectroscopic analysis method but also various methods for optically measuring and analyzing using laser light when measuring various properties in the combustion chamber of an internal combustion engine. For example, there is a method in which a fluorescent substance is mixed in the fuel, and when the fuel mixed with the fluorescent substance is injected into the combustion chamber, a laser beam is applied to emit light to measure the degree of diffusion of the fuel.
[0007]
Also in the above example, the laser light passes through the combustion chamber and is irradiated onto the wall surface of the combustion chamber. If scattered light is generated in the combustion chamber at this time, the visibility of the injected fuel emitted by the laser light is lowered.
[0008]
In view of these problems, the present invention prevents the laser light, which is irradiated in the combustion chamber of an internal combustion engine and used for measuring various properties in the combustion chamber, from being scattered light in the combustion chamber and obstructing the measurement. The problem is to prevent it.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a visualization window provided on a wall constituting the cylinder of an internal combustion engine, a light emitting unit that supplies light into a combustion chamber through the visualization window provided on the wall, The light irradiated from the light emitting unit is opened on the inner wall surface of the cylinder through which the visualization window and the combustion chamber are irradiated, and the opening area is larger than the light irradiation area, and the light incident from the opening is inside. An in-cylinder observation device for an internal combustion engine including a cutting portion formed so as to repeat reflection a plurality of times.
[0010]
In the in-cylinder observation device, the visualization window provided on the wall constituting the inside of the cylinder is formed of a high-strength and light-transmitting substance such as quartz glass, and the inside of the cylinder when the fuel is burning in the cylinder It enables visual recognition and measurement light to enter the cylinder. The light emitting unit emits high-intensity light having strong directivity such as laser light. Then, this light enters the cylinder as the measurement light through the visualization window.
[0011]
Moreover, the cutting part is formed so that incident light repeats reflection several times inside. This is because when the incident light is reflected by the inner surface of the cutting part, the intensity of the reflected light is attenuated due to the low reflectivity of the inner surface of the cutting part. The intensity of the measurement light is attenuated by being incident on the part and reflecting a plurality of times.
[0012]
The laser beam irradiated from the light emitting portion and passed through the inside of the tube reaches and is irradiated with the other inner wall surface of the cylinder opposite to the one wall surface through which the laser beam has been provided. At this time, the cutting portion is provided so that the irradiated surface is within the opening of the cutting portion of the wall surface. Since the irradiation surface is within the opening of the cutting part, scattered light due to the reflection of the laser light is not generated at the opening position of the cutting part.
[0013]
The laser light is light having a single wavelength and directivity in a single direction. However, when the laser light is irradiated onto a material having irregularities on the surface, scattered light is generated by the irregularities. Since the laser light originally has a high output, the illuminance of the scattered light easily exceeds the range allowed by the measuring instrument used for measurement in the combustion chamber, and may possibly damage the measuring instrument. Therefore, as described above, the laser beam is converged and attenuated in the cutting portion.
[0014]
The cutting part can be formed from a V-shaped groove that opens at an acute angle toward the inner wall surface of the cylinder with the deepest part of the cutting part as an apex, or a conical recess.
[0015]
When measuring light is irradiated to the cutting part composed of the V-shaped groove or the conical concave part with the acute angle of the opening with the deepest part of the cutting part as an apex, the measuring light irradiated to the cutting part is Reflected toward the apex on the inner surface of the cutting part. Since the reflection is repeated a plurality of times, the intensity of the measurement light is attenuated. Theoretically, the measurement light is repeatedly reflected inside the cutting part, and eventually radiated to the outside from the opening part. However, the angle of the opening part is set to an acute angle to increase the number of reflections. As a result of the attenuation, intense scattered light caused by the measurement light is not formed when irradiated outside the cutting part.
[0016]
When an ignition plug serving as an ignition device at the time of combustion is provided in the combustion chamber, the cutting portion can be provided on the wall surface of the ignition plug exposed in the cylinder.
[0017]
The purpose of irradiating the combustion chamber with laser light is to grasp the behavior of the combustion that occurs in the combustion chamber and the flow of fuel used for the combustion. Therefore, the shape of the combustion chamber is desirably the same shape as the combustion chamber of the internal combustion engine that is actually used. On the other hand, the cutting part provided in order to attenuate a laser beam is not necessarily required when using an internal combustion engine for an actual machine. Therefore, it is desirable that the configuration and shape of the fuel chamber wall surface, which are determinative factors for forming the combustion chamber, be not changed as much as possible. In other words, it is desirable to provide a cutting portion on the wall surface of the combustion chamber so as not to disturb the intake air flow or the like flowing through the combustion chamber.
[0018]
The ignition plug that protrudes into the combustion chamber and becomes the ignition device with respect to the shape of the combustion chamber wall surface, which becomes a determinant factor for forming the combustion chamber, is installed in a detachable state after the combustion chamber is formed. The shape also does not show a single shape. That is, the influence exerted by the shape of the spark plug in configuring the combustion chamber becomes an uncertain factor in specifying the behavior of the airflow and the like in the combustion chamber. Therefore, a change in behavior such as airflow due to a change in the shape of the spark plug is not necessarily an essential factor in grasping the behavior characteristics in the combustion chamber. Therefore, even if a cutting portion is provided on the wall of the spark plug that faces the combustion chamber, the influence of the cutting portion on the combustion chamber can be handled within the range of the influence of the spark plug on the combustion chamber.
[0019]
The spark plug is screwed and fixed to a wall of the combustion chamber, and one surface of the cutting part is formed to be opened at a screwed position between the spark plug and the wall of the combustion chamber. When fixed, a threaded portion provided at a threaded portion of the wall of the combustion chamber can be one surface of the cutting portion.
[0020]
The spark plug is screwed with the spark plug as a male screw and the wall constituting the combustion chamber as a female screw. The threaded portion can be regarded as an aggregate of valley-like grooves in terms of shape. Therefore, one surface of the cutting part provided in the spark plug is opened to the screw part. Thereby, when the spark plug is screwed with the wall constituting the combustion chamber, one surface of the surface constituting the cutting portion is constituted by the female screw portion of the wall constituting the combustion chamber. As a result, the laser light applied to one surface of the cutting portion made of the female screw portion is reflected on the female screw surface and attenuated in the same manner as the laser light is attenuated by the cutting portion provided in the valley shape. Is possible.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
Embodiment 1 will be described below. In the first embodiment, a component analysis is performed with a Raman spectrometer using a laser beam in order to analyze a component generated when a mixture of fuel and air burns in a combustion chamber of an internal combustion engine. is there.
[0022]
As shown in FIG. 1, the internal combustion engine 1 used in the first embodiment is a spark ignition type internal combustion engine that ignites an air-fuel mixture using an ignition plug 5 that is an ignition device and burns it. The internal combustion engine 1 is formed in a cylindrical shape inside, the cylinder is joined to the cylinder block 2 serving as a side wall of the combustion chamber, and the cylinder block 2 above, and a part of the lower wall is formed in the combustion chamber. A cylinder head 3 serving as an upper wall of the main body 10 is formed as a main driving body.
[0023]
A cylinder liner 4 is fitted into a cylinder provided in the cylinder block 2 to form a side surface of the combustion chamber 10. A piston 6 is inserted into the cylinder liner 4, and a combustion chamber 10 is formed from the upper surface of the piston 6, the inner surface of the cylinder liner 4, and the lower surface of the cylinder block 2. Further, quartz glass 7 is fitted into a part of the cylinder liner 4 and the cylinder block 2, and the inside of the combustion chamber is visible from the quartz glass 7 portion.
[0024]
Further, the quartz glass 11 is also fitted from the combustion chamber surface of the piston 6 to the pin boss surface which is a connecting portion to the connecting rod 8. A mirror 9 is installed below the piston 6, and the mirror 9 is irradiated with a laser beam to be reflected toward the quartz glass 7 located on the pin boss surface, and the inside of the combustion chamber 10 from the quartz glass 11 provided on the piston 6. Can be irradiated with laser light.
[0025]
The quartz glasses 7 and 11 are made of silicon dioxide made by melting pure silica and have a softening point of 1500 ° C. or higher, strong against temperature changes such as rapid quenching and high corrosion resistance. is there. Therefore, even when fuel burns in the combustion chamber 10, the inside of the combustion chamber 10 can be observed without being damaged.
[0026]
The cylinder head 3 is provided with an intake valve 16 that sucks air-fuel mixture into the combustion chamber 10, an exhaust valve 17 that discharges exhaust gas after combustion, and an ignition plug 5 that ignites the air-fuel mixture sucked into the combustion chamber 10. ing. As shown in FIGS. 2 and 3, the spark plug 5 is provided with a valley-shaped cutting portion 12 with a surface facing the combustion chamber as an opening. The cutting portion 12 is opened to a screw portion 19 that is a screwed portion of the spark plug 5 and the cylinder head 3. After the spark plug 5 is screwed to the cylinder head 3, the screw portion of the cylinder head 3 is turned to the cutting portion. 12 becomes a part of the inner surface. Further, a pressure detector 13 for detecting the pressure in the combustion chamber 10 is provided in the vicinity of the cutting portion 12, and the pressure change in the combustion chamber 10 when the air-fuel mixture burns is measured.
[0027]
The cutting portion 12 provided on the inner surface of the ignition plug 5 is a portion irradiated with laser light that passes through the quartz glass 7 provided on the piston 6 and is guided into the combustion chamber 10. The opening portion is drilled larger than the irradiation area irradiated with the laser beam.
[0028]
Hereinafter, Raman spectroscopic measurement, which is measurement performed in the first embodiment, will be described. The Raman spectroscopic measurement is spectroscopic analysis based on a Raman spectrum that appears due to the Raman effect. The Raman effect is the observation of the scattered light generated when the sample molecules are irradiated with monochromatic light such as laser light. The scattered light having the same frequency as the incident laser light is It is that weak scattered light (Raman light) having slightly different frequencies is generated.
[0029]
Since the deviation between the frequency of Raman light and the frequency of monochromatic light is a quantity specific to the substance, the type of substance to be measured depends on the deviation between the frequency of Raman light and the frequency of monochromatic light. It becomes possible to specify. Further, since the intensity of the Raman light is directly proportional to the measured amount of molecules, it is possible to calculate the measured amount of molecules according to the intensity of Raman light.
[0030]
When measuring the Raman light, the spectroscope 21 or the like is used to select the Raman light having a specific frequency, and the intensity of the selected Raman light is measured by the CCD camera 22 attached to the spectroscope 21. .
[0031]
The laser beam used in this measurement is high-intensity light composed of unit phases. When the spectroscope 21 and the CCD camera 22 are incident with intense light, the elements provided therein may be destroyed, and measurement may become impossible. Therefore, the light incident on the spectroscope 21 passes through a slit formed from a diffraction grating or the like that blocks light of a specific frequency and enters the light receiving portion of the spectroscope 21.
[0032]
The laser light travels straight as light having a single wavelength and a single period unless the material is irradiated and reflected. However, when reflected by a substance, it becomes light of various wavelengths and periods on the reflecting surface. Since the light is originally high in intensity, the reflected laser light becomes intense scattered light composed of light of various wavelengths. Since the scattered light is composed of various wavelengths, it cannot be blocked by a slit that blocks only light of a single wavelength, and inevitably enters the light receiving unit of the spectrometer 21. Since the incident scattered light is an aggregate of light of various wavelengths as described above, the light received by the spectroscope 21 includes Raman light indicating a specific wavelength as shown in the graph A of FIG. Near the same wavelength or light of the same wavelength. Thereby, the laser light is irradiated to the molecules in the combustion chamber 10 and it becomes difficult to specify the Raman light generated from the molecules.
[0033]
Therefore, the scattered light is reduced. The cause of the scattered light is that the scattered light spreads radially from the irradiation position of the laser light that passes through the combustion chamber 10 and is applied to the inner surface of the combustion chamber. In order to suppress the scattered light that diffuses radially, the irradiation position of the laser light provided on the spark plug 5 is a trough-shaped cutting part 12. As shown in FIG. 5, most of the laser beam irradiated and reflected on one surface of the valley that forms the cutting portion 12 is irradiated on the other surface of the valley that similarly forms the cutting portion 12. The laser beam reflected from the one surface and applied to the other surface is reflected from the other surface and applied to the other surface. Since the reflectance of the surface forming the cutting part 12 is low, the laser light irradiated to the cutting part 12 attenuates after being repeatedly reflected in the cutting part 12 a plurality of times.
[0034]
In the first embodiment, the cutting part 12 is provided on the inner surface of the combustion chamber of the spark plug 5. The cutting portion 12 is drilled so that the deepest portion of the cutting portion 12 is sufficiently deep. In the first embodiment, the combustion chamber surface of the spark plug 5 protrudes from the combustion chamber surface of the cylinder head 3. Since the cutting portion 12 is formed in the end portion of the surface of the combustion chamber of the spark plug 5, the side surface is open to the screw portion. When the spark plug 5 is attached to the cylinder head 3, the joint surface of the cylinder head 3 with the spark plug 5 forms one surface of the inner surface of the cutting portion 12. However, since the spark plug 5 is attached so as to protrude from the inner surface of the combustion chamber of the cylinder head 3, the protruding portion has a shape that does not have a side surface of the cutting portion 12. Therefore, as shown in FIG. 2, the light shielding plate 18 is provided at the protruding portion so that the reflected laser light does not leak from the cutting portion 12.
[0035]
Further, in the example shown in FIG. 6, the cutting portion 12 is provided so that one surface is opened in the screw portion direction of the cylinder head 3, and one inner surface of the cutting portion 12 is configured by the screw portion of the cylinder head 3. The As shown in FIG. 6, the screw portion is formed from a continuous uneven surface having a mountain shape and a valley shape. Since each of these concavo-convex surfaces is an inclined surface of a predetermined angle, when this screw portion is irradiated with a part of the laser beam incident and reflected in the cutting portion 12, it is provided on the screw portion. Due to these uneven surfaces, the reflection of the laser light is repeated and can be attenuated.
[0036]
Based on the above configuration, component analysis generated in the combustion chamber of the internal combustion engine is performed by a Raman spectrometer. Laser light used for this Raman spectroscopic measurement is irradiated by a known laser oscillation device 26. The irradiated laser light is converged into a narrower luminous flux through the lens 25, then reflected by a mirror 27 provided below the piston 6, and through 11 parts of quartz glass which is a visualization window provided in the piston 6. Irradiated into the combustion chamber 10. At this time, in the combustion chamber 10, a process is performed in which the air-fuel mixture mixed with air and fuel, which flows from the intake valve 16, is compressed, ignited and burned, and is exhausted from the exhaust valve 17. Therefore, the laser light that has flowed into the combustion chamber 10 is irradiated into the air-fuel mixture before combustion or the air-fuel mixture after combustion, and emits Raman light corresponding to each gas component.
[0037]
Thereafter, the laser light reaches the cutting portion 12 provided in the spark plug 5 protruding into the combustion chamber 10 and is irradiated on the inner surface of the cutting portion 12. By irradiating the inner surface provided in this valley shape, the laser light repeatedly attenuates reflection in the cutting portion 23. Therefore, the scattered light due to the laser light is not so much generated in the combustion chamber 10.
[0038]
Further, the Raman light generated by irradiating the molecules in the combustion chamber 10 with the laser light is irradiated to the outside from the quartz glass 7 portion which is a visualization window provided in the cylinder liner 4 and the cylinder block 2 on the side wall of the combustion chamber. The The irradiated Raman light passes through the slit 24 and blocks the light having the wavelength of the laser light, then passes through the lens 23 and is converged on the light receiving portion of the spectroscope 21. Then, the wavelength and intensity of Raman light are measured by the spectroscope 21 and the CCD camera 22, and the intensity of the wavelength indicated by a specific molecule is shown as shown in the graph B of FIG. Since the intensity of Raman light depends on the amount of molecules present, the ratio and amount of molecules present in the combustion chamber are calculated from the graph B shown in FIG. 5, and the component analysis by the Raman spectrometer is completed.
[0039]
(Embodiment 2)
Next, as a second embodiment, a description will be given of the fuel injected in the combustion chamber and the sheet-like laser light used when measuring the airflow. The test for measuring the spray state of the fuel injected into the combustion chamber is called an LIF test, in which a fluorescent substance is mixed in the fuel, and this fuel is injected into the combustion chamber. Then, the injected fuel is irradiated with a laser beam, and the trend of the injected fuel at each time is measured.
[0040]
The test for measuring the state of the airflow in the combustion chamber is called a PIV test, and a low specific gravity fine powder is mixed in the intake air flowing from the intake valve. Then, the intake air mixed with the fine powder is introduced into the combustion chamber, laser light is irradiated in this state, and the state of the airflow in the combustion chamber is measured by measuring the trend of the fine powder.
[0041]
In any of the tests, a sheet-like laser beam is irradiated into the combustion chamber, and a fuel or a gas stream containing fine powder emitted by the laser beam is photographed and analyzed. Therefore, when the laser beam is irradiated onto the wall surface and scattered light is generated, not only photographing is impossible, but the scattered light may damage the light receiving portion of the CCD camera. Therefore, it is necessary to reduce scattered light.
[0042]
FIG. 7 shows a view around the combustion chamber in the second embodiment. In the second embodiment, the cylinder block 32 that forms the side wall of the combustion chamber 40 is formed of quartz glass, and sheet-like laser light can be irradiated into the combustion chamber 40 from the side of the combustion chamber 40. A piston 36 is inserted from below into the combustion chamber 40 in which this quartz glass is formed as a side wall.
[0043]
The quartz glass forming the cylinder block 32 around the combustion chamber 40 allows the sheet-like laser light to pass through the combustion chamber 40 and serves as an irradiation location of the laser light that has passed through the combustion chamber 40. If the irradiated portion formed of this quartz glass is in a state where there is no adhesion of impurities or the like, the scattered light due to the laser light is transmitted without much from its high light transmission performance. However, when the measurement is performed, the fuel mixed with the fluorescent material or the air flow mixed with fine powder adheres, and the permeation performance is lowered. In this case, scattered light is generated, making the inside of the combustion chamber 40 unobservable. Therefore, the trough-shaped cutting part 42 is formed in the inner wall surface of the combustion chamber 40 used as the laser beam irradiation location.
[0044]
Since the laser beam is irradiated from one direction, a valley-shaped cutting part 42 is formed on the inner surface of the combustion chamber in the opposite direction. The formed cutting portion 42 is irradiated with laser light, and the laser light is attenuated.
[0045]
In the second embodiment, the shape in which the traveling direction of the laser light is irradiated into the combustion chamber from the direction perpendicular to the movement direction of the piston 36 has been described. In addition, as shown in FIG. 8, there is a method in which quartz glass 41 is fitted into the piston 36, and a sheet-like laser beam is guided into the combustion chamber from below the piston 36 to measure the combustion chamber. At this time, a trough-shaped cutting portion 42 is formed in the cylinder head 33, and the cutting portion 42 is irradiated with a sheet-like laser beam to converge and attenuate.
[0046]
(Embodiment 3)
Next, as Embodiment 3, a laser ignition test in which laser light guided into a combustion chamber is converged by a lens or the like to form a focal point in the combustion chamber, and fuel in the combustion chamber is ignited by heat generated at the focal point will be described. To do.
[0047]
As a conventional ignition device, there is an ignition plug 5 provided near the center of the cylinder head 3 as shown in FIG. This spark plug 5 is a method of igniting fuel with a spark generated when charging is performed between a cathode and an anode projecting into a combustion chamber and discharging using an onboard storage battery.
[0048]
On the other hand, laser ignition is a technique in which high-power laser light is converged by a lens and the fuel is ignited by the high temperature generated at the focal point. When this laser ignition is carried out experimentally, in order to investigate the combustion properties, quartz glass is used for the wall forming the combustion chamber so that it can be observed from the outside.
[0049]
Since the laser beam is condensed by the lens, it is dispersed after the temperature becomes high at the focal point. However, since the combustion chamber is narrow, before the laser beam is dispersed, the wall forming the combustion chamber is irradiated, and the dispersed light is emitted at the irradiated portion. The intense light that is the dispersed light makes it impossible to observe the inside of the combustion chamber. Therefore, it is necessary to suppress dispersed light. Therefore, a cutting part is provided on the surface where the laser beam is irradiated into the combustion chamber.
[0050]
As shown in FIG. 9, a part of the inner wall of the cylinder head 53, which is a wall that includes the intake valve 66 and the exhaust valve 67 and constitutes the combustion chamber 60, serves as a laser light irradiation location. A spindle-shaped cutting part 62 is drilled at the irradiated portion. The laser beam is applied to the opening of the spindle-shaped cutting part 62 and is repeatedly reflected and irradiated within the cutting part 62 to converge and attenuate. By attenuation, the inside of the combustion chamber 60 is not irradiated with scattered light caused by laser light, and the inside of the combustion chamber 60 can be observed.
[0051]
As described above, in each of the embodiments, the laser beam can be converged and attenuated by the valley-shaped or spindle-shaped cutting portion provided at the irradiation position of the laser beam without the laser beam emitting confusion light. .
[0052]
In addition, the cutting portion provided at this time has a trough-shaped or weight-shaped angle that forms the cutting portion in advance so that incident laser light is reflected and does not leak outside. Here, if the angle of the cutting part is not so acute, the incident laser light leaks to the outside of the cutting part in the course of reflection, and is scattered light outside the cutting part, in this embodiment, inside the combustion chamber. Even if a cutting part is provided, the effect cannot be fully achieved.
[0053]
【The invention's effect】
According to the present invention, it is possible to prevent the laser light that is irradiated into the combustion chamber of the internal combustion engine and used when measuring various properties in the combustion chamber from being scattered in the combustion chamber and inhibiting the measurement. Become.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an internal combustion engine and a measuring device according to Embodiment 1 of the present invention.
FIG. 2 is a side view of the ignition plug according to the first embodiment.
3 is a side view of the combustion chamber of the ignition plug according to Embodiment 1. FIG.
FIG. 4 is a graph showing the wavelength and intensity of measured light according to the first embodiment.
FIG. 5 is a conceptual diagram showing light emitted to a cutting portion according to the first embodiment.
FIG. 6 is a schematic view around a cutting portion and a screw portion according to the first embodiment.
FIG. 7 is a schematic view around a combustion chamber according to a second embodiment of the present invention.
FIG. 8 is a schematic view around a laser beam irradiation position according to the second embodiment.
FIG. 9 is a schematic view around a laser beam irradiation position according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder block 3 Cylinder head 4 Cylinder liner 5 Spark plug 6 Piston 7 Quartz glass 8 Connecting rod 9 Mirror 10 Combustion chamber 11 Quartz glass 12 Cutting part 13 Pressure detection part 16 Intake valve 17 Exhaust valve 18 Light shielding plate 19 Screw part 21 Spectroscope 22 CCD camera 23 Lens 23 Cutting section 24 Slit 25 Lens 26 Laser oscillator 27 Mirror 32 Cylinder block 33 Cylinder head 36 Piston 40 Combustion chamber 41 Quartz glass 42 Cutting section 53 Cylinder head 60 Combustion chamber 62 Cutting section 66 Intake valve 67 Exhaust valve

Claims (4)

A visualization window provided on a wall constituting the cylinder of the internal combustion engine;
A light emitting section for supplying light into the combustion chamber through a visualization window provided on the wall;
The light irradiated from the light-emitting unit is opened on the inner wall surface of the cylinder irradiated through the visualization window and the combustion chamber, and the light incident from the opening is internally opened. And an in-cylinder observation device for an internal combustion engine, including a cutting portion formed to repeat reflection multiple times. 2. The cylinder of the internal combustion engine according to claim 1, wherein the cutting portion is formed by a V-shaped groove or a conical recess opening at an acute angle toward the inner wall surface of the cylinder with the deepest portion of the cutting portion as an apex. Internal observation device. In the combustion chamber, an ignition plug is provided as an ignition device at the time of combustion,
The in-cylinder observation device for an internal combustion engine according to claim 1, wherein the cutting portion is provided on a wall surface of the spark plug exposed to the inside of the cylinder. The spark plug is screwed and fixed to the wall of the combustion chamber, and one surface of the cutting portion is formed to be opened at a screwing position between the spark plug and the wall of the combustion chamber.
The in-cylinder observation device for an internal combustion engine according to claim 3, wherein when the ignition plug is fixed, a screw portion provided at a screwing position of a wall of the combustion chamber becomes one surface of the cutting portion.

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