JP2007064037A - Ignition system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition system for an internal combustion engine, which can ignite the lean air fuel mixture with a remarkably small amount of light energy. <P>SOLUTION: The ignition system for the internal combustion engine ignites the air fuel mixture by a photocatalyst using the light energy emitted from a light generating device. The ignition system for the internal combustion engine is provided with a combustion chamber, the photocatalyst set in the combustion chamber, and the light generating device to irradiate the photocatalyst with the light energy. The ignition system for the internal combustion engine ignites the air fuel mixture with the photocatalyst using the light energy emitted from the light generating device. The ignition system for the internal combustion engine is provided with the combustion chamber, the photocatalyst set in the combustion chamber, and the light generating device to flatly irradiate the photocatalyst with the light energy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ignition system for an internal combustion engine, and more particularly to an ignition system for an internal combustion engine that ignites an air-fuel mixture by a photocatalyst using light energy emitted from a light generator.

One means for improving fuel efficiency is to improve thermal efficiency. Examples of means for improving the net thermal efficiency include increasing the compression ratio and dilution of the air-fuel mixture.
As for the dilution of the air-fuel mixture, the stability of combustion deteriorates as the mixture is diluted. Therefore, by generating a strong gas flow such as swirl and tumble in the combustion chamber and improving the flame propagation speed, It shortens the period and stabilizes combustion.
As for the spark plug, iridium is used to reduce the diameter of the electrode discharge part and improve wear resistance in order to ensure ignition stability.

The combustion is stabilized by shortening the flame propagation distance by multi-point ignition.
Regarding multi-point ignition, a technique using a laser that can stably ignite a strong gas flow instead of a conventional spark plug has been reported (see Patent Documents 1 and 2).
JP 58-195074 A Japanese Unexamined Patent Publication No. 63-173852

However, since the ignition devices described in Patent Documents 1 and 2 both ignite an air-fuel mixture in a space, it is necessary to irradiate with a high energy density light beam in focus.
Further, when the beam splitter is used, it is necessary to install the reflecting mirrors for the portion to be ignited inside, and the same number of condensing lenses is necessary, which causes a problem that the system becomes large.
Furthermore, since there is an intake / exhaust valve, there is a problem that there is a limit to the location where the light generator can be installed.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide an ignition system for an internal combustion engine that can ignite a lean air-fuel mixture with a significantly small amount of light energy. There is to do.

  As a result of intensive research to achieve the above object, the present inventors irradiate the photocatalyst with light energy from the light generator, activate the photocatalyst, and generate radicals necessary for ignition of the air-fuel mixture. Therefore, the present inventors have found that the above object can be achieved and have completed the present invention.

  That is, an ignition system for an internal combustion engine according to the present invention is an ignition system for an internal combustion engine that ignites an air-fuel mixture by a photocatalyst using light energy emitted from a light generator, and includes a combustion chamber and a combustion chamber. It is provided with the provided photocatalyst and the light generator which irradiates light energy with respect to this photocatalyst.

  In a preferred embodiment of the ignition system for an internal combustion engine of the present invention, the light generator irradiates the photocatalyst with light energy in a planar shape.

  According to the present invention, the photocatalyst is irradiated with light energy from the light generator, the photocatalyst is activated, and radicals necessary for ignition of the air-fuel mixture are generated using the photocatalytic reaction. It is possible to provide an ignition system for an internal combustion engine that can ignite a lean air-fuel mixture with an amount of light energy, and further an ignition system for an internal combustion engine that can improve fuel efficiency by lean combustion.

Hereinafter, an ignition system for an internal combustion engine of the present invention will be described.
As described above, the ignition system for an internal combustion engine of the present invention ignites an air-fuel mixture by a photocatalyst using light energy emitted from a light generator, and is provided in a combustion chamber and the combustion chamber. A photocatalyst and a light generator for irradiating the photocatalyst with light energy.
With such a configuration, for example, HC and O ₂ radicals can be generated using a photocatalytic reaction, and the mixture can be ignited with a significantly small amount of light energy.
In addition, it is possible to provide an ignition system for an internal combustion engine that can improve fuel efficiency by lean combustion.

Moreover, in this invention, it is desirable for the light generator provided with to irradiate light energy with respect to the photocatalyst with which it is provided planarly.
In this system, the photocatalyst is irradiated with light to generate electrons and holes on the surface of the photocatalyst, and these react with the air-fuel mixture to generate radicals and ignite the air-fuel mixture. For this reason, it is not necessary to focus as in the conventional laser ignition, and it is possible to increase the number of ignition points formed by the photocatalyst irradiated with light energy by irradiating light energy in a planar shape. As a result, combustion can be made more stable.
In addition, since light energy can be irradiated in a planar shape, it is not always necessary to use a plurality of light generators to increase the number of ignition points and perform multi-point ignition as described above. There is an advantage that the system can be reduced in size without being required.
Note that “irradiating in a planar manner” means irradiating so that the light energy irradiated by the light generator is not focused in the combustion chamber.

Furthermore, as a first preferred example of the arrangement of the photocatalyst in the present invention, when the provided combustion chamber is formed by a cylinder head and a piston head, the provided photocatalyst has a crown surface of the piston head, that is, the inside of the combustion chamber. The thing provided in the crown surface of the piston head which is a part of wall surface can be mentioned.
Specifically, it is possible to efficiently advance the photocatalytic reaction by forming a photocatalyst layer by applying or depositing a photocatalyst on the crown surface of the piston head, or by using a photocatalyst material for the piston itself. Become.

Furthermore, in the present invention, when the combustion chamber provided is formed by the cylinder head and the piston head, the crown surface of the piston head, that is, the crown surface of the piston head that is a part of the inner wall surface of the combustion chamber, It is desirable that many photocatalysts be provided on the side of the region where the air-fuel mixture concentration on the crown surface is relatively high.
For example, when the photocatalyst layer is formed on the crown surface of the piston head, the air-fuel mixture can be efficiently dispersed by increasing the coverage of the photocatalyst layer on the crown surface in the region where the gas mixture concentration is relatively high. Can be ignited.
Note that the air-fuel mixture concentration on the crown surface of the piston head is normally relatively high at the intake port provided in the combustion chamber, that is, the side facing the intake valve.

Further, as a second preferred example of the arrangement of the photocatalyst in the present invention, when the provided combustion chamber is formed by the cylinder head and the piston head, the cylinder head has a convex portion on its inner wall surface, and is provided. The thing in which the photocatalyst was provided in the convex part can be mentioned.
By providing such a convex portion provided with a photocatalyst, the air-fuel mixture is ignited not only near the inner wall surface of the combustion chamber, such as the inner wall surface of the cylinder head or the crown surface of the piston head, but also near the center portion of the combustion chamber. And the flame propagation distance can be shortened.
As a result, lean combustion can be performed more stably.
Note that the “convex portion provided on the inner wall surface of the cylinder head” is not limited to the normal intake / exhaust valves and pistons in the combustion chamber and can withstand high-temperature and high-pressure conditions with sudden fluctuations. The size and shape are not particularly limited, but, for example, a so-called jig having an L-shaped shape in which one end is fixed to the fuel chamber wall and the photocatalyst can be installed in the light irradiation direction. Can be mentioned.

Furthermore, as a third preferred example of the arrangement of the photocatalyst in the present invention, when the combustion chamber provided is formed by a cylinder head and a piston head, the piston head has another convex portion on the crown surface. , And a photocatalyst provided on the other convex portion.
By providing another convex part with such a photocatalyst, the mixture is ignited not only near the inner wall surface of the combustion chamber, such as the inner wall surface of the cylinder head or the crown surface of the piston head, but also near the center of the combustion chamber. And the flame propagation distance can be shortened.
As a result, as described above, lean combustion can be performed more stably.
In addition, “the other convex portion provided on the crown surface of the piston head” can prevent the intake and exhaust valves and pistons in the combustion chamber from moving, and can withstand high-temperature and high-pressure conditions with sudden fluctuations. The size and shape are not particularly limited. For example, not only columnar or spindle-shaped protrusions, but also those having appropriate through holes and having a shape like a soot. It can also be mentioned.

Furthermore, as a fourth preferred example of the arrangement of the photocatalyst in the present invention, the photocatalyst is provided with a mesh carrier having an end joined to the inner wall surface of the combustion chamber inside the combustion chamber. Can be mentioned.
By providing such a mesh-shaped carrier provided with a photocatalyst, the air-fuel mixture is ignited not only near the inner wall surface of the combustion chamber, such as the inner wall surface of the cylinder head or the crown surface of the piston head, but also near the center of the combustion chamber. And the flame propagation distance can be shortened.
As a result, as described above, lean combustion can be performed more stably.
The “mesh-shaped carrier” is not particularly limited in size and shape as long as it can withstand high-temperature and high-pressure conditions with rapid fluctuations without impeding the movement of intake and exhaust valves and pistons in the combustion chamber. Although not intended, for example, a mesh carrier having an opening having a size that is difficult to hinder gas flow in the combustion chamber can be used.

Moreover, in this invention, a part of inner wall surface of a combustion chamber can mention what functions as a mirror surface.
By providing a part that functions as a mirror surface on the inner wall surface of the combustion chamber, the irradiated light energy is reflected, the reflected light energy is irradiated to another part, and a photocatalyst is provided at the other part. Thus, for example, many dispersed locations can be used as ignition locations.
As a result, the flame propagation distance can be shortened, and lean combustion can be performed more stably.
In order to make a part of the inner wall surface of the combustion chamber function as a mirror surface, for example, a metal such as an aluminum alloy applied to a piston head, a cylinder head, or an intake / exhaust valve head may be mirror-finished, It is not limited to this.

Further, in the present invention, when the provided combustion chamber is formed by the cylinder head and the piston head, the optical axis direction of the light energy emitted by the provided light generating device is not parallel to the reciprocating direction of the provided piston head. Is desirable.
Specifically, it is desirable that the angle formed by the optical axis direction and the crown surface of the piston head is an acute angle.
When the optical axis direction and the reciprocating direction of the piston head are parallel, in other words, when the angle formed by the optical axis direction and the crown surface of the piston head is a right angle, other than the crown surface of the piston head, that is, the cylinder It is difficult to use the inner wall surface of the head as an ignition point, which is not desirable from the viewpoint of shortening the flame propagation distance.

Moreover, in this invention, when the combustion chamber with which it is provided is formed with the cylinder head and the piston head, it is desirable for the light generator provided to irradiate the light energy to the edge part of the crown surface of the piston head.
When the photocatalyst is provided at the end, the air-fuel mixture can be ignited by irradiating light energy in this way.
On the other hand, even when the photocatalyst is not provided at the end, by irradiating the light energy in this way, the end of the crown surface of the piston head is relatively low temperature, so it can be warmed up. More stable lean combustion can be performed.

Furthermore, in the present invention, it is desirable that the light generating device provided includes an irradiation position adjusting means.
By providing such an irradiation position adjusting means, the position where the light energy is applied can be adjusted as appropriate, and more stable lean combustion can be performed.

Furthermore, in the present invention, the combustion chamber provided is formed by a cylinder head and a piston head, and further includes temperature detection means for detecting the temperature of the combustion chamber, and the temperature detected by the temperature detection means is equal to or lower than a predetermined temperature. In this case, it is desirable that the irradiation position adjusting means provided adjusts the irradiation position so that light energy is irradiated to the end portion of the crown surface of the piston head that is a part of the inner wall surface of the combustion chamber.
By adopting such a configuration, it is possible to perform lean combustion more efficiently and more stably.
The “predetermined temperature” can be appropriately determined by experiments or the like.

Here, an example of a light generation apparatus provided with an irradiation position adjusting means for adjusting a position (region) where light energy is irradiated will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing a schematic cross-sectional shape of a laser oscillator with an irradiation position variable unit, which is an example of a light generation apparatus provided with an irradiation position adjusting means.
As shown in the figure, a laser oscillator 50 with an irradiation position variable unit includes a resonance portion 52 and an irradiation position variable unit 54 which is an example of an optical system. The irradiation position variable unit 54 includes a pair of front and rear transparent glasses. (54a, 54b), a concave lens 54c disposed between them, a lot 54d for coupling them, and a condenser lens 54e.
The light L extracted from the resonance portion 52 is transmitted through the transparent glass 54a, the concave lens 54c, the transparent glass 54b, and the condenser lens 54e in this order, and is irradiated to a photocatalyst (not shown).
The laser oscillator 50 can control the light energy irradiation region by moving the concave lens 54c back and forth in the direction along the lot 54d by an actuator (not shown).
In FIG. 1, the resonance portion 52 is disposed in the vicinity of the irradiation position variable unit 54, but although not shown, it is possible to transmit laser light using, for example, an optical fiber, so that both are arranged apart from each other. It is also possible to provide them, and the positional relationship when they are arranged is arbitrary.

FIG. 2 shows a state in which light energy is irradiated onto the crown surface of the piston head on which the photocatalyst layer is formed using a laser oscillator with an irradiation position variable unit.
FIG. 4A shows a case where light energy is irradiated at one point with a focus, and FIG. 4B shows a case where light energy is irradiated in a planar shape without focusing.
The extracted light L from the laser oscillator 50 with the irradiation position variable unit is irradiated to the photocatalyst C provided on the crown surface of the piston head.
In addition, (theta) in the figure (a) shows the angle | corner which the optical axis direction of optical energy and the crown surface of a piston head make. Moreover, A in the figure (b) shows an irradiation area | region.

Here, specific elements constituting the internal combustion engine ignition system of the present invention will be described.
First, the internal combustion engine applied to the ignition system of the present invention only needs to obtain power by burning the air-fuel mixture, such as fuel, operation system, cycle, number of cylinders, cylinder type, cooling system, valve mechanism, number of valves, etc. Is not particularly limited. Furthermore, it is applicable also to a rotary engine.

  Next, the photocatalyst used for the internal combustion engine ignition system of the present invention is, for example, a porous titanium oxide, zinc oxide, niobium oxide, tantalum oxide or tin oxide, and any combination thereof. However, it is not limited to these.

  Next, the air-fuel mixture applied to the internal combustion engine ignition system of the present invention is not particularly limited, but typically, fuel gas (gasoline, light oil, natural gas, alcohol, etc.) and air are arbitrarily selected. It is obtained by blending.

Next, as a light generator used in the internal combustion engine ignition system of the present invention, for example, a laser oscillator can be used.
As such a laser oscillator, a solid laser, a gas laser, a semiconductor laser, an excimer laser, a free electron laser, or the like can be used alone or in combination as appropriate, although it varies depending on the type of gas mixture or photocatalyst to be burned.
Moreover, a conventionally well-known thing can be used as an optical system apparatus of this laser oscillator. Note that when igniting the air-fuel mixture, it is possible to ignite with a small amount of light energy, so it is not always necessary to focus, and therefore a condensing lens is not necessarily required. Is possible.

  Hereinafter, the present invention will be described in more detail with reference to some examples, but the present invention is not limited to these examples.

Example 1
FIG. 3 is an explanatory diagram showing a schematic cross-sectional shape of the ignition system for the internal combustion engine of the present example.
As shown in the figure, the internal combustion engine ignition system 1 of this example includes a combustion chamber 10 formed by a cylinder head 12 and a piston head 14, and a photocatalyst 20 provided on the crown surface of the piston head 14 of the combustion chamber 10. And a laser oscillator 30 which is an example of a light generator that irradiates the photocatalyst 20 with light energy.
The cylinder head 12 has a window 12a, and the light energy irradiated from the laser oscillator 30 passes through the window 12a and is irradiated to the photocatalyst 20 as shown in FIG. The irradiated photocatalyst 20 becomes an ignition location and ignites the air-fuel mixture in the combustion chamber 10.
The air-fuel mixture is obtained from the fuel supplied from the injection 12c provided in the intake port 12b and the intake air, and is supplied to the combustion chamber 10 by opening the intake valve 12d. Further, after the air-fuel mixture burns, the exhaust valve 12e is opened and exhausted as combustion gas from the exhaust port 12f.

Thus, since it became possible to ignite with less light energy than before using the photocatalyst, it is possible to ignite in a wider area.
As a result, combustion became stable, lean combustion became possible, and the lean combustion region was expanded.

It is explanatory drawing which shows schematic cross-sectional shape of a laser oscillator with an irradiation position variable unit. It is explanatory drawing which shows a mode that light energy is irradiated with respect to the piston head crown surface in which the photocatalyst layer was formed using the irradiation position variable unit. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a schematic cross-sectional shape of an internal combustion engine ignition system according to a first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ignition system for internal combustion engines 10 Combustion chamber 12 Cylinder head 12a Window 12b Intake port 12c Injection 12d Intake valve 12e Exhaust valve 12f Exhaust port 14 Piston head 20 Photocatalyst 30 Laser oscillator 50 Laser oscillator with irradiation position variable unit 52 Resonant part 54 Irradiation position Variable unit 54a, b Transparent glass 54c Concave lens 54d Lot 54e Condensing lens

Claims (12)

An internal combustion engine ignition system for igniting an air-fuel mixture with a photocatalyst using light energy emitted from a light generator,
An internal combustion engine ignition system comprising: a combustion chamber; a photocatalyst provided in the combustion chamber; and a light generator that irradiates the photocatalyst with light energy.   The ignition system for an internal combustion engine according to claim 1, wherein the light generator irradiates the photocatalyst with light energy in a planar shape.   The internal combustion engine ignition system according to claim 1 or 2, wherein the combustion chamber is formed by a cylinder head and a piston head, and the photocatalyst is provided on a crown surface of the piston head.   The combustion chamber is formed by a cylinder head and a piston head, and a large amount of the photocatalyst is provided on the crown side of the piston head on the region side where the mixture concentration on the crown surface is relatively high. The ignition system for an internal combustion engine according to any one of claims 1 to 3.   The combustion chamber is formed by a cylinder head and a piston head, the cylinder head has a convex portion on its inner wall surface, and the photocatalyst is provided on the convex portion. 5. The ignition system for an internal combustion engine according to any one of 4 above.   The combustion chamber is formed by a cylinder head and a piston head, the piston head has another convex portion on a crown surface thereof, and the photocatalyst is provided on the other convex portion. The ignition system for an internal combustion engine according to any one of claims 1 to 5.   The inside of the said combustion chamber has a mesh-shaped support | carrier by which the edge part was joined to the inner wall face of the said combustion chamber, The said photocatalyst was provided in this mesh-shaped support | carrier. An ignition system for an internal combustion engine according to any one of the items.   The ignition system for an internal combustion engine according to any one of claims 1 to 7, wherein a part of the inner wall surface of the combustion chamber functions as a mirror surface.   The combustion chamber is formed by a cylinder head and a piston head, and an optical axis direction of light energy emitted by the light generator is not parallel to a reciprocating direction of the piston head. 9. The ignition system for an internal combustion engine according to any one of items 8 to 9.   10. The combustion chamber according to claim 1, wherein the combustion chamber is formed by a cylinder head and a piston head, and the light generator irradiates light energy to an end portion of a crown surface of the piston head. An ignition system for an internal combustion engine according to one item.   The ignition system for an internal combustion engine according to any one of claims 1 to 10, wherein the light generation device includes an irradiation position adjusting unit.   When the combustion chamber is formed by a cylinder head and a piston head and includes a temperature detection means for detecting the temperature of the combustion chamber, the irradiation is performed when the temperature detected by the temperature detection means is equal to or lower than a predetermined temperature. The ignition system for an internal combustion engine according to claim 11, wherein the position adjusting means adjusts the irradiation position so that light energy is irradiated to an end of the crown surface of the piston head.

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