JPH11324879A - Internal combustion engine - Google Patents

Abstract

(57) [Problem] To provide an internal combustion engine capable of decomposing an organic substance such as lubricating oil or unburned fuel which causes a deposit to avoid generation of a deposit on a surface of a combustion chamber or the like. SOLUTION: A titanium oxide layer 20 with a silicon film 22 as a base is coated on the surface of a part constituting an inner surface of a combustion chamber 4, such as a crown surface of a piston 2, an inner surface of a cylinder head 3, and the like, while a spark plug 7 is provided. The ignition is performed in the combustion chamber 4 by performing a multi-stage ignition operation of spark ignition for mixture ignition in the compression stroke and spark ignition for photocatalytic activity of the titanium oxide layer 20 in the exhaust stroke. The combustion light causes the photocatalytic reaction of the titanium oxide layer 20, and the discharge light of the ignition plug 7 activates the photocatalytic reaction of the titanium oxide layer 20 even in the exhaust stroke, whereby organic substances such as soot, unburned fuel, and lubricating oil are decomposed. Thus, the deposit on the inner surface of the combustion chamber 4 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an internal combustion engine mounted on a vehicle such as an automobile.

[0002]

2. Description of the Related Art Some internal combustion engines are disclosed in, for example,
As disclosed in Japanese Patent No. 05352, a combustion chamber of an internal combustion engine is constituted by a member having a ceramic coating layer containing a lithium element, a titanium coating layer, a magnesium coating layer, a coating layer containing an alkali-resistant metal, and the like on the surface. By
There has been known an apparatus which suppresses deposit accumulation on the surface of the combustion chamber.

[0003]

However, in the above-mentioned prior art, soot generated by combustion of the air-fuel mixture in the combustion chamber, lubricating oil entering the combustion chamber, or unburned fuel remains on the combustion chamber. Deposition of the deposits generated by the deposition depends only on a decrease in the adhesion of the deposits due to a ceramic coating layer or the like provided on the metal surface of the part constituting the combustion chamber. When a precursor that becomes a nucleus to adhere to is generated, deposition of the deposit proceeds rapidly, and deterioration of combustion due to a change in the volume of the combustion chamber, deterioration of combustion due to mixture ignition before ignition by a spark plug, and There is a possibility that a problem such as an increase in exhaust components such as unburned HC generated and discharged from the fuel tank may occur.

Therefore, the present invention provides an effect of decomposing organic substances such as lubricating oil and unburned fuel which cause deposits.
An object of the present invention is to provide an internal combustion engine capable of avoiding generation of deposits on the surface of a combustion chamber.

[0005]

According to the first aspect of the present invention, the surface of a component constituting the inner surface of the combustion chamber is coated with a titanium oxide layer based on a silicon film.
The ignition plug performs a multi-stage ignition operation of spark ignition for mixture ignition in a compression stroke and spark ignition for photocatalytic activity of the titanium oxide layer in an exhaust stroke. I have.

According to a second aspect of the present invention, the ignition operation in the exhaust stroke of the ignition plug according to the first aspect is performed by a long-time ignition device for performing a long-time spark discharge. Features.

According to a third aspect of the present invention, the ignition operation in the exhaust stroke of the ignition plug according to the first aspect is performed by a multiple-type ignition device that repeats a short-time spark discharge in a required ignition period. It is characterized by doing.

According to a fourth aspect of the present invention, the ignition operation in the exhaust stroke of the ignition plug according to the first aspect is performed continuously from the expansion stroke.

According to a fifth aspect of the present invention, the ignition operation from the expansion stroke to the exhaust stroke of the spark plug according to the fourth aspect is performed by a multiple ignition device that repeats a short-time spark discharge in a required ignition period. It is characterized in that it is performed.

According to the invention of claim 6, claims 1 to 5 are provided.
The ignition final timing of the ignition plug in the exhaust stroke described in (1) is set immediately before a new air-fuel mixture is formed in the combustion chamber.

According to the invention of claim 7, claims 1 to 6 are provided.
Wherein the inner surface of the exhaust port following the combustion chamber is coated with a titanium oxide layer based on a silicon film.

According to an eighth aspect of the present invention, an inner surface of the exhaust manifold following the exhaust port according to the seventh aspect is coated with a titanium oxide layer based on a silicon film.

[0013]

According to the first aspect of the present invention, the light generated by the combustion of the air-fuel mixture in the combustion chamber can provide a photocatalytic effect by the titanium oxide layer provided on the inner surface of the combustion chamber, thereby causing a deposit. Organic substances such as lubricating oil and unburned fuel are decomposed and generated on the inner surface of the combustion chamber, or deposits that are being generated can be easily separated, and in the exhaust stroke where combustion light tends to decrease. Also, since the ignition operation of the ignition plug is performed and discharge light is generated, the photocatalytic action of the titanium oxide layer is actively performed even in this exhaust stroke, and it is possible to thoroughly prevent the deposition of deposits on the inner surface of the combustion chamber.

According to the invention described in claim 2, according to claim 1,
In addition to the effect of the invention, the ignition operation in the exhaust stroke of the ignition plug is performed by a long-time ignition device by performing a long-time spark discharge. Therefore, the discharge light of the ignition plug is maintained long in the exhaust stroke. In particular, when discharging is performed for a long time in the exhaust stroke, the pressure around the spark plug is low during this exhaust stroke, and the discharge voltage of the spark plug becomes a function of the in-cylinder pressure. Since the peak voltage is reduced, a large amount of subsequent discharge energy remains and discharge can be reliably maintained for a long time, and the discharge energy increases as the in-cylinder pressure decreases due to the progress of the exhaust stroke. Since the light can be intensified, the photocatalytic action of the titanium oxide layer can be surely and more actively performed over the end of the exhaust stroke.

According to the invention described in claim 3, according to claim 1 of the present invention,
In addition to the effects of the invention, the ignition operation in the exhaust stroke of the ignition plug is made to repeatedly perform a short-time spark discharge in a required ignition period by the multiple ignition device. Since the discharge light is obtained intermittently for a required period of time and the discharge energy increases as the in-cylinder pressure decreases due to the progress of the exhaust stroke, the discharge light is strengthened. The photocatalysis of the layer can be reliably and more actively performed.

According to the invention described in claim 4, according to claim 1 of the present invention,
In addition to the effect of the invention, the ignition operation in the exhaust stroke of the spark plug is performed continuously from the expansion stroke, so that the ignition probability to the air-fuel mixture can be increased and the stable combustion can be performed. The light emission required for the photocatalytic action of the titanium oxide layer can be continuously present from the expansion stroke to the exhaust stroke, and the photocatalytic action of the titanium oxide layer is reliably and actively activated from the expansion stroke to the exhaust stroke. Can be performed.

According to the invention described in claim 5, according to claim 4,
In addition to the effects of the invention, the ignition operation from the expansion stroke of the spark plug to the exhaust stroke is repeated by a multiplexed ignition device for a short period of spark discharge in a required ignition period. The discharge light of the ignition plug is obtained intermittently for a required period of time during the exhaust stroke, and the discharge energy increases as the in-cylinder pressure decreases due to the progress from the expansion stroke to the end of the exhaust stroke. As a result, the photocatalytic action of the titanium oxide layer can be surely and more actively performed from the expansion stroke to the end of the exhaust stroke.

According to the invention of claim 6, according to claim 1,
In addition to the effects of the fifth to fifth aspects, the final ignition timing of the spark plug in the expansion stroke is set immediately before a new air-fuel mixture is formed in the combustion chamber. Can be secured.

According to the invention of claim 7, according to claim 1,
In addition to the effects of the inventions of (1) to (6), the inner surface of the exhaust port following the combustion chamber is also coated with a titanium oxide layer based on a silicon film. The generated light exerts a photocatalytic action on the titanium oxide layer, and an effect of suppressing deposit adhesion on the inner surface of the exhaust port due to the adhesion of soot and unburned fuel is obtained.

According to the invention described in claim 8, according to claim 7,
In addition to the effect of the invention, since the inner surface of the exhaust manifold following the exhaust port is also coated with a titanium oxide layer based on a silicon film, it is generated by combustion even in the exhaust manifold where late combustion is maintained. The photocatalytic action of the titanium oxide layer is exerted by the light, and an effect of suppressing the adhesion of deposits on the inner surface of the exhaust manifold due to the adhesion of soot and unburned fuel is obtained.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, 1 is a cylinder block, 2
Represents a piston, 3 represents a cylinder head, and 4 represents a combustion chamber formed by the cylinder block 1, the piston 2, and the cylinder head 3.

As shown in FIG. 2, titanium oxide 2 is provided on the surfaces of components constituting the inner surface of the combustion chamber 4, specifically, the crown surface of the piston 2 and the inner surface of the cylinder head 3.
A titanium oxide layer 20 having a silicon coating 22 as a base is formed by applying a silica sol mixed with the fine particles of No. 1 and baking it, and the titanium oxide layer 20 is irradiated with light generated by combustion of an air-fuel mixture in the combustion chamber 4. At 20, a photocatalytic reaction occurs.

As the titanium oxide 21 used for forming the titanium oxide layer 20, fine particles of anatase type crystal having the highest photoactive ability, more preferably fine particles having a particle size of 1 to 20 nm, may be used.

If the particle size of the titanium oxide 21 is smaller than the above range, the fine particles of the titanium oxide 21 will be agglomerated when stirred with the silica sol. The photoactivity of the compound is extremely reduced.

On the other hand, the filling ratio of the silica sol containing the fine particles of titanium oxide 21 is preferably 5 to 40%.

In order to obtain the adhesion between the titanium oxide layer 20 and metal surfaces such as the crown surface of the piston 2 and the inner surface of the cylinder head 3 and the uniformity and durability of the coating of the titanium oxide layer 20, It is necessary that the filling ratio is 5% or more, and if the filling ratio exceeds 40%, poor photoactivity of the titanium oxide 21 occurs.

The titanium oxide layer 20 is baked at a temperature of 300 ° C. or more at which the silica sol is converted into a resin. At a high temperature of 700 ° C. or more, the crystal of the titanium oxide 21 changes from an anatase type to a rutile type. It is important to bake at a temperature lower than 700 ° C.
When 0 is provided on the aluminum parts such as the piston 2 and the cylinder head 3 as described above, the upper limit of the firing temperature is set to 350 ° C. to 400 in consideration of the heat resistance of these aluminum parts.
It is desirable to be set to ° C.

When the titanium oxide layer 20 is formed on the crown surface of the piston 2 and the inner surface of the cylinder head 3 in this manner, the molecules generated in the combustion process of the air-fuel mixture are specified in the combustion chamber 4 as shown in FIG. There is light emission of a wavelength, and in particular, ultraviolet light emission of a wavelength of about 400 nm or less at which the action of the photocatalyst of titanium oxide 21 becomes active is generated. Organic substances such as lubricating oil components are decomposed by the photocatalytic reaction of the titanium oxide 21.

FIG. 8 shows the results of gas chromatographic analysis of the adhesion of organic substances on the crown surface of the piston 2 with and without the titanium oxide layer 20 when the engine was operated under the same conditions. (B)
As shown in the figure, the detection time was 9.6 minutes, 14.3 minutes, 1
6.4 minutes, 18.1 minutes, 19.6 minutes, 23.2 minutes, 2
Hydrocarbon (HC) with a large number of molecules in each time zone of 4.4 minutes
However, in the case of the titanium oxide layer treatment, hydrocarbon (HC) was not detected as shown in (a) of the figure, and the photocatalytic function in the titanium oxide layer 20 on the piston 2 crown surface was exhibited. You can see that.

On the other hand, FIG. 9 shows the analysis results of detecting metal components on the piston crown surfaces of the treated and untreated titanium oxide layer 20. FIG. ) Indicates a titanium oxide layer-treated product. In each case, calcium (Ca) and phosphorus (P) characteristic of a lubricating oil component are detected on the crown surface of the piston 2 in substantially the same manner.

From the results of these analyses, at least the lubricating oil was treated with the treated titanium oxide layer 20 and the untreated piston 2.
Although it adheres to the crown surface, it can be seen that hydrocarbons (HC) are decomposed and cleaned in the treated product of the titanium oxide layer 20.

The above-described lubricating oil enters the combustion chamber 4 along the sliding surface between the piston 2 and the cylinder block 1, and therefore, the adhesion of the lubricating oil also occurs on the crown surface of the piston 2, the outer peripheral portion thereof, and the cylinder. There is a tendency that the annular region near the boundary between the head 3 and the cylinder bore increases.

Therefore, it is effective to provide the titanium oxide layer 20 only on the outer peripheral portion of the crown surface of the piston 2 and the annular region near the boundary of the cylinder head 3 with the cylinder bore.

The umbrella portions 5a and 6a of the intake valve 5 and the exhaust valve 6 are arranged in the combustion chamber 4 and the ignition plug 7 is arranged in a protruding manner.
The ignition plug 6 and the spark plug are also components constituting the inner surface of the combustion chamber 4.

Therefore, by providing the titanium oxide layer 20 also on the intake and exhaust valves 5 and 6 and the ignition plug 7 as described above, the measures for deposits in the combustion chamber 4 become more effective.

With respect to the intake valve 5 and the exhaust valve 6, the titanium oxide layer 20 may be formed only on the surface of each umbrella portion 5a, 6a on the side of the combustion chamber 4, but as shown in FIG. It is desirable to provide a titanium oxide layer 20 on the surface and the portions exposed to the intake port 8 and the exhaust port 9 of each of the stems 5b and 6b.

As for the spark plug 7, as shown in FIG. 4, a titanium oxide layer 20 is formed on a metal portion other than the discharge surface of the center electrode 7a and the ground electrode 7b.

As described above, by providing the titanium oxide layer 20 on the intake and exhaust valves 5 and 6, organic substances such as soot and unburned fuel are removed from the surfaces of the umbrella portions 5 a and 6 a on the combustion chamber 4 side. As described above, it is decomposed by the photocatalytic reaction in the titanium oxide layer 20 to obtain the effect of suppressing the adhesion of the deposit. Similarly, the surface of the intake valve 5 on the intake port 8 side of the fuel that enters the combustion chamber 4 from the intake port 8. The effect of suppressing the adhesion of the deposit due to the adhesion, and the adhesion of the deposit due to the adhesion of unburned fuel and soot in the combustion gas flowing out from the combustion chamber 4 to the exhaust port 9 on the surface of the exhaust valve 6 on the exhaust port 9 side. An inhibitory effect is obtained, and these absorptions,
The stick of the exhaust valves 5 and 6 can be avoided.

Further, in the spark plug 7, the presence of the titanium oxide layer 20, as described above, makes it possible to avoid deposits around the discharge surface of the spark plug 7.

Since a metal head gasket 10 is interposed between the cylinder block 1 and the cylinder head 3, a gap corresponding to the thickness of the head gasket 10 is provided between the cylinder block 1 and the cylinder head 3. A quench (extinguishment) gap C is generated.

Therefore, by forming the titanium oxide layer 20 also on the surface of the quench gap C as shown in FIG. 5, a comprehensive countermeasure against deposits in the combustion chamber 4 can be taken.

That is, as described above, if the quench gap C exists at the joint between the cylinder block 1 and the cylinder head 2, lubricating oil or fuel enters the gap C and causes a deposit. However, the organic substance that enters the quench gap C and adheres to the surface is the titanium oxide layer 20.
Is decomposed by the photocatalytic reaction in the, and the accumulation of deposits is avoided.

In the cylinder injection type spark ignition engine, a fuel injection valve 11 is provided in the combustion chamber 4 as shown by a broken line in FIG.

Therefore, in such a direct injection type spark ignition engine, the portion of the fuel injection valve 11 exposed in the combustion chamber 4 as shown in FIG.
0 is formed.

By forming the titanium oxide layer 20 on the exposed portion of the combustion chamber of the fuel injection valve 11 as described above, the deposit on the tip of the fuel injection valve caused by the adhesion of soot and fuel after injection or lubricating oil is obtained. Adhesion control effect is obtained,
In addition to ensuring thorough measures against deposits in the combustion chamber 4,
It is possible to avoid a change in the fuel injection angle, the fuel injection amount, and the like caused by the deposit attached to the tip portion of the fuel injection valve, thereby improving the stability of combustion and the output.

On the other hand, the combustion gas in the combustion chamber 4 is exhausted to the exhaust port 9 in the exhaust stroke. However, the combustion is continued in the exhaust port 9 and the exhaust manifold 12 following the exhaust port 9, and the photocatalytic reaction of titanium oxide occurs. Effective combustion light is emitted.

Therefore, a titanium oxide layer 20 is formed on the inner surfaces of the exhaust port 9 and the exhaust manifold 12 in the same manner as described above as shown in FIG. In addition, the photocatalytic action of the titanium oxide layer 20 is exhibited also in the exhaust manifold 12, and it is possible to prevent the accumulation of deposits due to the adhesion of soot and unburned fuel, to avoid the influence on the in-cylinder pressure and to improve the combustion stability and Output can be improved and harmful exhaust components can be reduced.

According to the present invention, as described above, the silicon coating 2 is formed on the surface of each of the components constituting the inner surface of the combustion chamber 4 and on the inner surfaces of the exhaust port 9 and the exhaust manifold 12.
In addition to providing a titanium oxide layer 20 having a base layer 2 as a base so as to exhibit a photocatalytic action, the ignition plug 7 is used for spark ignition for mixture ignition in a compression stroke and the combustion in the exhaust stroke. A multi-stage ignition operation, such as spark ignition for photocatalytic activity of the titanium oxide layer 20 on the inner surface of the chamber 4, is performed.

The multi-stage ignition operation of the ignition plug 7 is as follows.
It is controlled by the ignition device 23 shown in FIG.

FIGS. 10 to 14 show different examples of the ignition timing of the ignition plug 7 by the ignition device 23. FIG.

In the first embodiment shown in FIG.
Are set in multiple stages at a first ignition timing P ₁ in the latter half of the compression stroke and a second ignition timing P ₂ in the latter half of the exhaust stroke, and spark ignition for mixture ignition in the latter half of the compression stroke is performed. In the latter stage of the exhaust stroke, spark ignition for photocatalytic activity of the titanium oxide layer 20 on the inner surface of the combustion chamber 4 is performed.

Therefore, according to the first embodiment, after the air-fuel mixture is spark-ignited by the ignition operation of the ignition plug 7 in the compression stroke, the combustion light is generated by the combustion light generated by the combustion of the air-fuel mixture in the expansion stroke as described above. Titanium oxide layer 20 inside chamber 4
On the other hand, in the exhaust stroke in which the combustion light tends to decrease, when the piston 2 rises and approaches the ignition plug 7, the ignition plug 7 is activated again to generate discharge light. Also in this exhaust stroke, the photocatalytic action of the titanium oxide layer 20 can be actively performed, and therefore, the deposit on the inner surface of the combustion chamber 4 can be thoroughly prevented.

In the first embodiment, since the ignition operation in the exhaust stroke of the ignition plug 7 is performed in the same manner as the ignition operation in the compression stroke, it is possible to realize the ignition device 23 without any special improvement. it can.

FIG. 11 shows a second embodiment of the ignition timing of the ignition plug 7. In this second embodiment, a long-time spark discharge is applied to the ignition plug 7 at the second ignition timing P ₂ in the exhaust stroke. The operation is controlled so that it is performed.

The long-time spark discharge control of the ignition plug 7 can be realized by using, for example, a long-time ignition device as disclosed in Japanese Patent Application Laid-Open No. 6-66236 as the ignition device 23.

As described above, the ignition operation in the exhaust stroke of the ignition plug 7 is performed by causing the long-time ignition device to perform a long-time spark discharge, thereby maintaining the discharge light of the ignition plug 7 long in the exhaust stroke. In particular, when discharging is performed for a long time in the exhaust stroke, the pressure around the ignition plug 7 is low in this exhaust stroke, and the discharge voltage of the ignition plug 7 becomes a function of the in-cylinder pressure. Since the initial peak voltage is reduced, a large amount of discharge energy thereafter remains, and the discharge can be maintained for a long time, and the discharge energy increases as the in-cylinder pressure decreases due to the progress of the exhaust stroke. Since the discharge light can be enhanced, the photocatalytic action of the titanium oxide layer 20 on the inner surface of the combustion chamber 4 can be surely and more actively performed over the end of the exhaust stroke.

[0058] Figure 12 shows a third embodiment of the ignition timing of the ignition plug 7, as this In the third embodiment, substantially the entire area of the exhaust stroke of the second ignition period of the ignition timing P ₂ in the exhaust stroke The ignition plug 7 is set and the ignition plug 7 is controlled so as to repeatedly perform short-time spark discharge during this ignition period.

The multiple discharge control of the ignition plug 7 during the required ignition period is performed, for example, by using the ignition device 23 as disclosed in
This can be realized by using a multiple ignition device as disclosed in Japanese Patent No. 30836.

As described above, the ignition operation in the exhaust stroke of the spark plug 7 is performed by repeatedly performing the spark discharge in a short time over substantially the entire exhaust stroke by the multiplex type ignition device, thereby performing the multiple discharges. As a result, the discharge light of the spark plug 7 is intermittently obtained, and as the in-cylinder pressure decreases due to the progress of the exhaust stroke, the discharge energy increases and the discharge light is strengthened. The photocatalytic action of the titanium oxide layer 20 on the inner surface of the combustion chamber 4
In addition, it can be made to be more active.

FIG. 13 shows a fourth embodiment of the ignition timing of the ignition plug 7. In this fourth embodiment, the ignition operation of the ignition plug 7 in the exhaust stroke is performed continuously from the expansion stroke. It was done.

In the fourth embodiment, specifically, the ignition device 2
The range from the latter stage of the compression stroke to the end of the exhaust stroke is set as a discharge period Pa by using the above-described multiple ignition device as 3, and the spark plug 7 is caused to repeatedly perform a short-time spark discharge in this discharge period Pa. Like that.

Therefore, according to the fourth embodiment, after the air-fuel mixture is spark-ignited by the ignition operation of the spark plug 7 in the latter stage of the compression stroke, the spark discharge of the spark plug 7 is subsequently performed in the ignition period Pa which is the end of the exhaust stroke. Is repeated in a short period of time, so that the ignition probability to the air-fuel mixture can be increased and stable combustion can be realized, and of course, the discharge light of the spark plug 7 is continuously emitted from the expansion stroke to the end of the exhaust stroke. And the discharge energy increases as the in-cylinder pressure decreases due to the progress from the expansion stroke to the end of the exhaust stroke, and the discharge light is strengthened. The photocatalysis of the titanium oxide layer 20 on the inner surface of the combustion chamber 4 can be reliably and more actively performed over the final period.

In this multiple discharge control, for example, FIG.
It is also possible to make the discharge cycle in the discharge period Pa smaller by taking a longer unit discharge time as shown in FIG. 4 so that the discharge energy on the exhaust stroke side becomes higher and the discharge light becomes stronger on the exhaust stroke side. it can.

Here, no matter which of the above ignition timings is set, the final ignition timing of the ignition plug 7 is
It is important to set a value immediately before a new air-fuel mixture is formed in the combustion chamber 4 to avoid misfires and to ensure the stability of the engine. the engine intended to be set up just before the fuel injection fuel injection valve 11, the way, the ignition timing shown in FIG. 11 but ignition final timing of the second ignition period P ₂ is in delayed until early in the intake stroke, which is It is assumed that the case is adapted to a direct injection engine.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a titanium oxide layer in one embodiment of the present invention.

FIG. 3 is an explanatory diagram of intake and exhaust valves according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a spark plug according to one embodiment of the present invention.

FIG. 5 is a sectional view of a head gasket interposed portion according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram of a fuel injection valve according to one embodiment of the present invention.

FIG. 7 is an explanatory diagram showing wavelength characteristics of combustion light in a combustion chamber.

FIG. 8 is an explanatory view showing an analysis result of adhesion of an organic substance.

FIG. 9 is an explanatory diagram showing an analysis result of oil adhesion on a piston crown surface.

FIG. 10 is an explanatory diagram showing a first form of ignition timing of an ignition plug.

FIG. 11 is an explanatory diagram showing a second form of the ignition timing of the ignition plug.

FIG. 12 is an explanatory diagram showing a third form of the ignition timing of the ignition plug.

FIG. 13 is an explanatory diagram showing a fourth embodiment of the ignition timing of the ignition plug.

FIG. 14 is an explanatory diagram showing a fifth embodiment of the ignition timing of the ignition plug.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Piston 3 Cylinder head 4 Combustion chamber 5 Intake valve 6 Exhaust valve 7 Spark plug 8 Intake port 9 Exhaust port 10 Head gasket 11 Fuel injection valve 12 Exhaust manifold 20 Titanium oxide layer 21 Titanium oxide 22 Silicon coating

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 1/00 F02F 1/00 D 3/12 3/12

Claims (8)

[Claims] 1. The surface of a component constituting an inner surface of a combustion chamber,
While coating the titanium oxide layer with the silicon coating as the base, the spark plug is used for the spark ignition for the mixture ignition in the compression stroke and the spark ignition for the photocatalytic activity of the titanium oxide layer in the exhaust stroke. An internal combustion engine characterized in that a stepwise ignition operation is performed. 2. The internal combustion engine according to claim 1, wherein the ignition operation in the exhaust stroke of the ignition plug is performed by a long-time ignition device that performs a long-time spark discharge. 3. The internal combustion engine according to claim 1, wherein the ignition operation in the exhaust stroke of the ignition plug is performed by a multiplex ignition device that repeats a short-time spark discharge in a required ignition period. . 4. The internal combustion engine according to claim 1, wherein the ignition operation in the exhaust stroke of the spark plug is performed continuously from the expansion stroke. 5. The ignition system according to claim 4, wherein the ignition operation from the expansion stroke to the exhaust stroke of the spark plug is performed by a multiplex ignition device which repeats a short-time spark discharge in a required ignition period. An internal combustion engine as described. 6. The internal combustion engine according to claim 1, wherein the final ignition timing of the ignition plug in the exhaust stroke is set immediately before a new air-fuel mixture is formed in the combustion chamber. 7. The internal combustion engine according to claim 1, wherein an inner surface of an exhaust port following the combustion chamber is coated with a titanium oxide layer based on a silicon film. 8. The internal combustion engine according to claim 7, wherein an inner surface of the exhaust manifold following the exhaust port is coated with a titanium oxide layer based on a silicon film.