JP3837833B2 - In-cylinder internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique that enables stratified combustion under a wide range of operating conditions, particularly in a cylinder injection internal combustion engine in which fuel spray is directly injected into a cylinder and spark ignition is performed by an ignition plug.
[0002]
[Prior art]
Conventionally, as a cylinder injection internal combustion engine, for example, as disclosed in JP-A-6-207542, during stratified combustion operation, fuel spray is injected toward the cavity on the top surface of the piston at the end of the compression stroke, Due to the synergistic effect of the swirling air flow (swirl) in the cylinder and the guide action on the cavity side wall, the fuel spray is efficiently transferred to the lower side of the spark plug to achieve stratification of the combustible mixture. What is possible is known.
[0003]
[Problems to be solved by the invention]
However, the transfer of the fuel spray to the lower side of the spark plug is controlled by the cavity shape of the piston top surface and the swirling air flow in the cylinder, so that when the engine operating conditions change, the swirling air flow in the cylinder Due to the change, it becomes difficult to stratify the combustible mixture below the spark plug, and stratified combustion may become impossible. For this reason, depending on the engine operating conditions, the swirl control valve provided in the intake port is opened and closed to control the swirling air flow in the cylinder in a complicated manner. However, such control is very difficult. The control of engine stratified combustion was extremely complicated.
[0004]
Accordingly, in view of the above-described conventional problems, the present invention provides a direct injection internal combustion engine that improves the formation method and the transfer method of the combustible mixture and enables stratified combustion under a wide range of operating conditions. The purpose is to do.
[0005]
[Means for Solving the Problems]
For this reason, the invention according to claim 1 directly injects fuel spray into the combustion chamber by the fuel injection valve disposed on the intake side wall surface of the combustion chamber formed between the piston top surface and the cylinder head lower surface. In a direct injection internal combustion engine that performs spark ignition with a spark plug disposed at a substantially central portion of a wall surface facing a piston top surface of a combustion chamber, a high pressure is applied to an exhaust side wall surface of the combustion chamber facing the fuel injection valve. An air injection valve for injecting air is disposed, and fuel spray injected from the fuel injection valve and high-pressure air injected from the air injection valve are prevented from diffusing to the surroundings on the piston top surface. A guide groove for guiding high pressure air to the substantially central portion of the piston is formed, and a fuel spray and high pressure air collide with each other at the substantially central portion of the guide groove to form a combustible mixture. It was to be transferred to the grayed down.
[0006]
When performing stratified charge combustion operation, fuel spray is injected from the fuel injection valve toward the guide groove at the end of the compression stroke, and high-pressure air is injected from the air injection valve toward the guide groove in synchronization with the fuel injection. . The fuel spray and the high-pressure air injected into the guide groove are respectively guided to the substantially central portion of the guide groove while being prevented from spreading to the surroundings by the inner wall of the guide groove. The fuel spray and high-pressure air collide at the approximate center of the guide groove, and the fluid friction or heat of the high-pressure air promotes vaporization of the fuel spray and formation of a combustible mixture, forming a locally combustible mixture. Is done. Then, the combustible air-fuel mixture is transferred below the spark plug where the guide groove opens, and is ignited by the spark plug to perform stratified combustion.
[0007]
On the other hand, when the homogeneous combustion operation is performed, fuel spray is injected from only the fuel injection valve toward the guide groove at the beginning of the intake stroke. The fuel spray injected into the guide groove is promoted by the tumble flow generated in the combustion chamber to promote the vaporization of the fuel spray and the formation of the combustible mixture, and spreads almost uniformly in the combustion chamber. Combustion takes place.
[0008]
Therefore, there is no need to control the swirling air flow in the cylinder in a complicated manner as in the past, and a mechanism for controlling the swirling air flow such as a swirl control valve is not required, reducing the cost by reducing the number of parts, and control. Costs can be reduced by simplifying the contents. In addition, the high-pressure air injected from the air injection valve actively promotes the vaporization of fuel spray and the formation of a combustible mixture, so that stratified combustion is performed under a wide range of operating conditions. Fuel consumption rate improves.
[0009]
According to a second aspect of the present invention, the guide groove extends in the injection direction of the fuel spray injected from the fuel injection valve and the high-pressure air injected from the air injection valve, and matches the spread of the fuel spray and the high-pressure air. The cross-sectional shape was formed.
If it does in this way, the fuel spray injected from the fuel injection valve will not adhere to the inner wall of a guide groove, and will be guided to the approximate center part of a guide groove, being controlled to spread to the circumference. On the other hand, the high-pressure air injected from the air injection valve is guided to the substantially central portion of the guide groove while suppressing diffusion to the surroundings, similarly to the fuel spray. Then, substantially the entire amount of the fuel spray and high-pressure air collide substantially at the center of the guide groove, and the fuel spray is vaporized and the formation of the combustible mixture is promoted efficiently. Further, since the adhesion of fuel spray to the inner wall of the guide groove is reduced, HC and the like contained in the exhaust gas are reduced, and the exhaust property is improved.
[0010]
According to a third aspect of the present invention, the piston top surface has a smooth edge portion.
In this way, during the homogeneous combustion operation, the tumble flow generated in the combustion chamber is reduced from being peeled off at the edge portion of the piston top surface, and the fully open performance of the engine is improved.
[0011]
According to a fourth aspect of the present invention, the air injection valve is configured to inject high-pressure air in synchronization with the fuel injection valve.
In this way, the injection timing of the high-pressure air of the air injection valve is synchronized with the injection timing of the fuel spray of the fuel injection valve, so the control of the air injection valve is simplified, and reliability and cost increases are minimized. It is suppressed.
[0012]
The invention according to claim 5 includes a brake booster that boosts the braking force, and an air compressor that compresses and supplies air, and the air compressor is taken out from the intake passage via the brake booster. The intake air is compressed and supplied to the air injection valve.
In this way, even when the negative pressure generated in the intake passage is small during the stratified combustion operation, a negative pressure is generated by the operation of the air compressor, and the brake booster is effective by using this negative pressure. Will work. Accordingly, it is not necessary to separately provide a negative pressure pump for operating the brake booster, and the cost can be reduced by reducing the number of parts.
[0013]
【The invention's effect】
As described above, according to the first aspect of the present invention, a mechanism for controlling the swirling air flow in the combustion chamber in a complicated manner is not necessary, and the cost can be reduced by reducing the number of components and the cost can be reduced by simplifying the contents of control. Can be achieved. In addition, the high-pressure air injected from the air injection valve actively promotes the vaporization of fuel spray and the formation of a combustible mixture, so that stratified combustion is performed under a wide range of operating conditions. The fuel consumption rate can be improved.
[0014]
According to the second aspect of the present invention, substantially the entire amount of the fuel spray and high-pressure air collides at the substantially central portion of the guide groove, so that it is possible to efficiently promote the vaporization of the fuel spray and the formation of the combustible mixture. it can. Further, since the adhesion of fuel spray to the inner wall of the guide groove is reduced, HC and the like contained in the exhaust gas can be reduced, and the exhaust property can be improved.
[0015]
According to the third aspect of the invention, during the homogeneous combustion operation, the tumble flow generated in the combustion chamber is reduced from being separated at the edge portion of the piston top surface, and the fully open performance of the engine can be improved.
According to the fourth aspect of the present invention, the control of the air injection valve is simplified, and a decrease in reliability and an increase in cost can be suppressed as much as possible.
[0016]
According to the fifth aspect of the present invention, it is not necessary to separately provide a negative pressure pump for operating the brake booster, and the cost can be reduced by reducing the number of parts.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an embodiment of a direct injection internal combustion engine of the present invention.
A combustion chamber 12 having a predetermined volume is formed between the top surface of the piston 10 (hereinafter referred to as “piston top surface”) 10 a and the lower surface of the cylinder head 11. An intake port 14 opened and closed by an intake valve 13 and an exhaust valve are provided on the wall surface of the cylinder head 11 located above the combustion chamber 12, that is, the wall surface of the cylinder head combustion chamber 12 a formed at the lower part of the cylinder head 11. Two exhaust ports 16 opened and closed by 15 are formed in parallel.
[0018]
An electronically controlled fuel injection valve 17 that injects fuel spray is injected between both intake ports 14 of the cylinder head 11, and high-pressure air is injected between both exhaust ports 16 of the cylinder head 11 facing the fuel injection valve 17. The electronically controlled air injection valves 18 are arranged so as to have a predetermined angle with respect to the piston top surface 10a. That is, the fuel injection valve 17 and the air injection valve 18 are disposed on substantially the same line. An ignition plug 19 that sparks and ignites a combustible mixture of fuel and air is disposed at a substantially central portion of the wall surface of the cylinder head combustion chamber 12a.
[0019]
Fuel that is pressurized by the high-pressure fuel pump 20 is supplied to the fuel injection valve 17 via a high-pressure fuel pipe 21. The fuel injection valve 17 is driven to open by the fuel injection valve drive unit 22 and injects a predetermined amount of fuel according to engine operating conditions. Reference numeral 23 in the figure is a high-pressure fuel pressure regulator that adjusts the fuel supplied to the fuel injection valve 17 to a predetermined pressure.
[0020]
Air that is pressurized by a high-pressure air compressor 24 (air compressor) is supplied to the air injection valve 18 via a high-pressure air pipe 25. The air injection valve 18 is driven to open by an air injection valve drive unit 26 and injects high-pressure air in synchronization with the fuel injection valve 17. Reference numeral 27 in the drawing denotes a high-pressure air pressure regulator that adjusts the pressure of the air supplied to the air injection valve 18 to a predetermined pressure.
[0021]
The high-pressure air compressor 24 is supplied with intake air taken out from the intake collector 28 via an air supply pipe 29. In the middle of the air supply pipe 29, a negative pressure tank 30 is interposed, from which negative pressure is supplied to a brake booster 31 (brake booster) that boosts the braking force.
By the way, in the cylinder injection internal combustion engine, during the stratified combustion operation, the negative pressure generated in the intake passage is small, and it is difficult to obtain the negative pressure for effectively operating the brake booster 31. Therefore, when the brake booster 31 is interposed between the intake collector 28 and the high pressure air compressor 24 via the negative pressure tank 30, a negative pressure is generated in the air supply pipe 29 by the operation of the high pressure air compressor 24. If negative pressure is utilized via the negative pressure tank 30, the brake booster 31 will operate | move effectively. Therefore, it is not necessary to separately provide a negative pressure pump for operating the brake booster 31, and the cost can be reduced by reducing the number of parts.
[0022]
Reference numeral 32 in the drawings not explained above is a main control unit with a built-in microcomputer, which controls the fuel injection valve drive unit 22 and the air injection valve drive unit 26 based on the engine operating state.
Further, as shown in FIG. 2, the piston top surface 10a extends in the injection direction of the fuel spray injected from the fuel injection valve 17 and the high-pressure air injected from the air injection valve 18, and the fuel spray and the high-pressure air A guide groove 10b having a transverse cross section is formed in accordance with the spread of. In other words, the guide groove 10b guides the fuel spray injected from the fuel injection valve 17 and the high-pressure air injected from the air injection valve 18 to the substantially central portion of the guide groove 10b while not diffusing to the surroundings. The fuel spray and the high-pressure air collide head-on at a substantially central portion of 10b. At this time, in order to prevent fuel spray from adhering to the inner wall of the guide groove 10b and increasing HC and the like in the exhaust gas, the cross-sectional shape of the guide groove 10b is formed larger than the spread of the fuel spray. On the other hand, with respect to the high-pressure air injected from the air injection valve 18, air does not adhere to the inner wall of the guide groove 10b. The guide groove 10b is formed in substantially the same shape as the side guide groove 10b.
[0023]
Next, the operation of the direct injection internal combustion engine having such a configuration will be described with reference to FIG.
At the end of the compression stroke during the stratified combustion operation, high-pressure air A is injected from the air injection valve 18 toward the guide groove 10b in synchronization with injection of the fuel spray F from the fuel injection valve 17 toward the guide groove 10b (FIG. 3 (a)).
[0024]
The fuel spray F and the high-pressure air A injected into the guide groove 10b are respectively guided to the substantially central portion of the guide groove 10b while being prevented from spreading to the surroundings by the inner wall of the guide groove 10b. The fuel spray F and the high-pressure air A collide front at a substantially central portion of the guide groove 10b, and the fluid friction or the heat of the high-pressure air promotes the vaporization of the fuel spray F and the formation of the combustible mixture M. A local combustible mixture M is formed (see FIG. 3 (b)).
[0025]
Then, the combustible mixture M is transferred below the spark plug 19 where the guide groove 10b is opened, and the combustible mixture M is stratified below the spark plug 19 (see FIG. 3 (c)).
Thereafter, the combustible mixture M is sparked by the spark plug 19 and stratified combustion is performed.
[0026]
Further, when the engine is operated at a high load, if the fuel spray is injected only from the fuel injection valve 17 at the beginning of the intake stroke, the tumble flow generated in the combustion chamber 12 promotes the vaporization of the fuel spray and the formation of the combustible mixture, A substantially uniform combustible air-fuel mixture is formed in the combustion chamber 12. The combustible air-fuel mixture is spark-ignited by the spark plug 19, and homogeneous combustion that generates high output is performed.
[0027]
In this way, the vaporization of the fuel spray and the combustible mixing can be performed by the high-pressure air injected from the air injection valve 18 without complicated control of the swirling air flow in the cylinder as in a conventional cylinder injection internal combustion engine. The formation of air is promoted, and the combustible air-fuel mixture is transferred below the spark plug 19 so that stratified combustion is performed under a wide range of operating conditions.
[0028]
This eliminates the need for a complicated control mechanism for the swirling air flow in the cylinder. For example, in the case of controlling the swirling air flow using a swirl control valve, the cost reduction is achieved by reducing the number of parts and simplifying the control. can do. In addition, since the region where the stratified combustion operation can be performed is expanded, the fuel consumption rate of the engine can be improved.
[0029]
In addition, as shown in FIG. 4, the piston top surface 10a may be formed with a smooth edge portion.
In this way, the tumble flow separated by the edge portion of the piston top surface 10a during the homogeneous combustion operation during the high load operation of the engine can be reduced, and the fully open performance of the engine can be further improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention. FIG. 2 shows an embodiment of the guide groove of the same, (a) is a top view, (b) is a cross-sectional view taken along line AA in (a), (c) is a cross-sectional view taken along the line BB in (a). [FIG. 3] Explains the operation of the above, (a) is a view immediately after fuel spray and high-pressure air are injected, and (b) is in the guide groove. FIG. 4 is a diagram showing the formation of a combustible mixture, FIG. 4C is a diagram showing the transfer of the combustible mixture to the lower side of the spark plug, FIG. 4 shows another embodiment of the guide groove, and FIG. b) is a cross-sectional view taken along the line CC in (a), and (c) is a cross-sectional view taken along the line DD in (a).
DESCRIPTION OF SYMBOLS 10 Piston 10a Piston top surface 10b Guide groove 11 Cylinder 12 Combustion chamber 12a Cylinder head combustion chamber 17 Fuel injection valve 18 Air injection valve 24 High pressure air compressor 31 Brake booster

Claims (5)

Fuel spray is directly injected into the combustion chamber by a fuel injection valve disposed on the intake side wall surface of the combustion chamber formed between the piston top surface and the cylinder head lower surface. In a cylinder injection internal combustion engine that performs spark ignition with a spark plug disposed in a substantially central portion,
An air injection valve for injecting high-pressure air is disposed on the exhaust side wall surface of the combustion chamber facing the fuel injection valve, and fuel spray injected from the fuel injection valve and injection from the air injection valve are applied to the piston top surface. A guide groove for guiding the fuel spray and the high-pressure air to the substantially central portion of the piston is formed while preventing the high-pressure air from diffusing to the surroundings, and the fuel spray and the high-pressure air collide at the substantially central portion of the guide groove. Thus, a combustible air-fuel mixture is formed, and the combustible air-fuel mixture is transferred below the spark plug. The guide groove extends in the injection direction of the fuel spray injected from the fuel injection valve and the high-pressure air injected from the air injection valve, and its cross-sectional shape is formed in accordance with the spread of the fuel spray and high-pressure air. The in-cylinder injection internal combustion engine according to claim 1, which has a configuration. The in-cylinder injection internal combustion engine according to claim 1 or 2, wherein the piston top surface has a configuration in which an edge portion thereof is smoothly formed. The in-cylinder injection internal combustion engine according to any one of claims 1 to 3, wherein the air injection valve is configured to inject high-pressure air in synchronization with the fuel injection valve. A brake booster that boosts the braking force, and an air compressor that compresses and supplies air,
The cylinder according to any one of claims 1 to 4, wherein the air compressor is configured to compress intake air taken out from an intake passage via the brake booster and supply the compressed air to the air injection valve. Internal injection type internal combustion engine.

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