JPH11351012A - Direct cylinder injection type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct cylinder injection type spark ignition engine that allows a desirable purge at stratified charge combustion and improves output at its high-speed and high-loaded operation. SOLUTION: A single cylinder is provided with three intake ports 5 (5a, 5b and 5c). The first or central intake port 5a is so shaped that an intake flow travels direct into a combustion-chamber cavity 2 defined in a piston 1, and is provided on its upstream side with a cutoff valve 12 and an evaporative emission purging outlet 14. The second and third intake ports 5b and 5c on both sides of the first intake port 5a are both so shaped that an intake flow generates a tumble flow in a combustion chamber 3. A variable valve system is provided to stop the operation of a third intake valve 7c for opening or closing the third intake port 5c. A cutoff valve opening/closing system 13 is provided to control the opening/closing of the cutoff valve 12, and a control unit 18 is installed to control fuel injection timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a direct cylinder injection type spark ignition engine.

[0002]

2. Description of the Related Art As a conventional direct in-cylinder injection type spark ignition engine, for example, FIGS. 21 to 23 (JP-A-5-79370).
Publication). This is piston 01
A concave combustion chamber cavity 02 formed on the top surface and a spark plug 04 inserted near the side wall of the combustion chamber cavity 02 at the time of ignition with the rise of the piston 01 are installed, and the intake port 05 is a helical intake port. It comprises a first intake port 05a to be formed and a second intake port 05b to form a straight type intake port extending straight. Each of the intake ports 05a and 05b is connected to a collector 011 via an intake passage 010 formed in the intake manifold, and is connected to the second intake port 05.
b in the second intake passage 010b leading to the intake control valve 01
2 are installed. Further, a high-pressure fuel injection valve 06 is provided obliquely downward with respect to the combustion chamber 03 below the intake port 05.
Is installed. In this conventional example, in a specific operation state, the swirl flow 09 gas flow is generated by the opening / closing control 013 of the intake control valve 012, and the fuel ignition plug 0
The stratification is about 4 and the fuel efficiency is improved by operating at an ultra-lean air-fuel ratio. Here, 07 is an intake valve, and 08 is an exhaust valve.

[0003]

However, in such a conventional direct in-cylinder injection spark ignition engine, it is necessary to form a strong swirl flow 09 during stratification. Since the strong swirl flow 09 cannot be formed only by closing the second intake port 05b, the first intake port 05a has a helical shape. For this reason, in the output region at the time of high rotation and high load, intake resistance occurs, and the output performance decreases. Further, when evaporative fuel is purged at the time of stratification, the purge gas is supplied to the first intake port 0 in the conventional stratified combustion using the gas flow of the swirl flow 09.
Since the fuel flows into the combustion chamber 03 along the swirl flow 09 via the gas flow 5a, the evaporative fuel is long outside the combustion chamber 03 and does not concentrate in the combustion chamber cavity 02 on the top surface of the piston 01. Therefore, it becomes difficult to perform combustion mixed with the injected fuel in the combustion chamber cavity 02, and the exhaust performance deteriorates. SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and it is possible to perform good purging at the time of stratified combustion and to improve the output at the time of high rotation and high load by direct in-cylinder injection. An object of the present invention is to provide a spark ignition engine.

[0004]

In order to achieve the above object, according to the first aspect of the present invention, three intake ports are formed for one cylinder and a center located at the center of the three intake ports. The first intake port is formed in such a shape that the flow of the intake air is directly directed to the recess of the piston, a shutoff valve is provided upstream of the central first intake port, and the outlet of the evaporative purge is provided at the central first intake port downstream of the shutoff valve. The second intake port and the third intake port located on both sides of the central first intake port are formed in such a shape that the flow of intake air generates a tumble flow in the combustion chamber, and the operation of an intake valve for opening and closing the third intake port. Variable valve mechanism that stops the engine according to the operating state, shut-off valve opening and closing mechanism that controls the opening and closing of the shut-off valve according to the operating state of the engine, and injection timing that controls the fuel injection timing according to the operating state of the engine Control means , Characterized in that it comprises a. According to the direct in-cylinder injection spark ignition engine according to the first aspect, the formation of a strong swirl flow during stratification and the formation of two forward tumble gas flows during weak stratification by controlling the opening and closing of each port according to the operating conditions. To achieve low swirl flow during homogeneous lean burn and low intake resistance in the output range at high speeds and high loads, and to improve fuel efficiency and fully open the throttle through ultra-lean air-fuel ratio operation by fuel injection at a specific time. It is possible to improve output performance by increasing air charging efficiency during operation. Also, when evaporating fuel is purged during stratification,
Since the gas can be introduced from the port and the gas flow in the combustion chamber can be controlled, the purge gas can be concentrated in the combustion chamber on the piston top surface, and the mixing with the injected fuel can be promoted in the combustion chamber, so that the combustion is improved. In addition, deterioration of exhaust performance can be prevented.

According to a second aspect of the present invention, in the direct in-cylinder injection spark ignition engine according to the first aspect, when the operating state of the engine is in an area where stratified charge combustion is performed near the spark plug to collect an air-fuel mixture. The variable valve mechanism stops the operation of the intake valve of the third intake port, the shutoff valve opening / closing mechanism closes the shutoff valve of the central first intake port, and the injection timing control means sets the fuel injection timing to the latter stage of the compression stroke. , Characterized in that. According to the direct in-cylinder injection type spark ignition engine according to the second aspect, in the stratified combustion region in the low-medium-speed, low-load region, the operating condition of the engine increases the gas flow in the cylinder and forms a strong swirl flow. By injecting the fuel at least in the latter stage of the compression stroke, stratification of the fuel around the ignition plug can be achieved, the fuel can be operated at an ultra-lean air-fuel ratio, and the fuel efficiency can be improved. , The fuel atomization and vaporization progress, and there is no misfire due to the adhesion of the liquid fuel to the ignition plug, and stable operation can be performed. Also, even when purging the evaporative fuel, the evaporative fuel is introduced directly from the central first intake port toward the combustion chamber on the piston top surface, so that the purge gas enters the combustion chamber on the piston top surface, which is the center of the swirl gas flow. Concentrate,
Mixing with the injected fuel in the combustion chamber enables stable combustion.

According to a third aspect of the present invention, in the direct in-cylinder injection spark ignition engine according to the first or second aspect, when the operating state of the engine is in a region where a weak stratified fuel for collecting an air-fuel mixture is provided near the spark plug. The variable valve mechanism operates the intake valve of the third intake port, the shut-off valve opening / closing mechanism closes the shut-off valve of the central first intake port, and the injection timing control means sets the fuel injection timing to the first half of the compression stroke. It is characterized by the following. Claim 3
According to the direct in-cylinder injection spark ignition engine described above, in the stratified combustion region in the low-medium-speed / medium-load region, the operating conditions of the engine slightly weaken the gas flow in the cylinder and the intake air entering the combustion chamber. The air produces two forward tumble flow gas flows and injects fuel at least during the first half of the compression stroke, resulting in a weak stratification that creates a band of fuel mixture in the middle of the two tumble flow gas flows. Driving at an air-fuel ratio can improve fuel efficiency. Also, when purging the evaporative fuel, the purge gas concentrates at the center of the two forward tumble flow gas flows, and mixes with the fuel mixture zone in the middle of the gas flows, enabling stable combustion.

According to a fourth aspect of the present invention, in the direct cylinder injection type spark ignition engine according to any one of the first to third aspects, the operating state of the engine forms a homogeneous lean mixture in the combustion chamber. The variable valve mechanism stops the intake valve of the third intake port, the shutoff valve opening / closing mechanism opens the shutoff valve of the central first intake port when the engine is in the region where the homogeneous lean combustion is performed, and the injection timing control means controls the fuel injection timing. Is set in the intake stroke. According to the direct in-cylinder injection spark ignition engine according to the fourth aspect, in a homogeneous lean burn region in a low-medium-speed / medium-load region, a strong swirl flow flows from the central first intake port. Attenuated by the flow of intake air entering the combustion chamber, fuel is injected at least during the intake stroke to achieve a homogenized fuel mixture and operate at a lean air-fuel ratio,
Fuel efficiency can be improved. When evaporative fuel is purged, the purge gas and the injected fuel are sufficiently mixed because the fuel injection is performed during the intake stroke, and stable combustion can be performed similarly to the conventional intake port fuel injection engine.

According to a fifth aspect of the present invention, in the direct in-cylinder injection spark ignition engine according to the first to fourth aspects, the operating state of the engine is in a region where homogeneous combustion is performed in which a homogeneous mixture is formed in the combustion chamber. At this time, the variable valve mechanism operates the intake valve of the third intake port, the shutoff valve opening and closing mechanism opens the shutoff valve of the central first port, and the injection timing control means sets the fuel injection timing to the intake stroke. Features. According to the direct in-cylinder injection spark ignition engine according to the fifth aspect, in the homogeneous combustion region in a high-speed / high-load region, the operating condition of the engine is to increase the intake port area to improve the charging efficiency and to reduce the fuel at least. By injecting during the intake stroke, the air-fuel mixture is homogenized, and sufficient performance can be ensured in the output region. Further, when purging the evaporative fuel, the purge gas and the injected fuel are sufficiently mixed because the fuel injection is performed during the intake stroke, and stable combustion can be performed similarly to the conventional intake port fuel injection engine.

According to a sixth aspect of the present invention, in the direct in-cylinder injection type spark ignition engine according to the first to fifth aspects, the central first intake port has a shape which stands upright with respect to the cylinder and points toward the recess of the piston. , The second intake port and the third intake port have a straight shape that generates a tumble flow in the combustion chamber. According to the direct in-cylinder injection type spark ignition engine according to claim 6, the flow flowing from the central first intake port is directed to the combustion chamber on the piston top surface,
Since the flows flowing from the second and third intake ports form forward tumbles, the required gas flow (the formation of a strong swirl flow during stratification, Formation of two forward tumble gas flows at the time of stratification, formation of a weak swirl flow at the time of homogeneous lean combustion, and low intake resistance in the output region at high rotation and high load).

According to a seventh aspect of the present invention, in the direct in-cylinder injection spark ignition engine according to the first to sixth aspects, a guide groove is formed in an upper wall of the central first intake port along a flow direction of intake air, The outlet of the evaporative purge is opened near the guide groove. According to the direct in-cylinder injection spark ignition engine described in claim 7, the operating conditions of the engine are a stratified combustion region in a low-medium speed / low load region and a weak stratified combustion region in a low-medium speed / medium load region. When purging evaporative fuel,
The evaporative fuel flows in the upper part of the central first intake port, mostly enters the combustion chamber on the top surface of the piston directly from the exhaust valve side opening of the first intake valve, and swirl gas flow or two forward tumbles Since more concentration occurs in the combustion chamber on the top surface of the piston located at the center of the flowing gas flow, mixing with the injected fuel is promoted in this combustion chamber, and stable combustion is possible.

According to the invention described in claim 8, in the direct in-cylinder injection spark ignition engine according to any one of claims 1 to 6, the lift amount of the intake valve that opens and closes the central first intake port is adjusted by the other second valve.
It is characterized in that it is set smaller than the intake valve that opens and closes the intake port or the third intake port. According to the direct in-cylinder injection spark ignition engine according to the eighth aspect, the operating condition of the engine is such that the third intake valve stops operating in the low-medium-speed / medium-load homogeneous homogeneous lean combustion region, and the first intake valve operates. And only the second intake valve is operated, and the shutoff valve in the first intake passage is opened, and the first intake valve and the second in the region where fuel is injected at least during the intake stroke, and the homogeneous combustion region where high speed and high load are applied. In the region where the intake valve and the third intake valve are operated, and the shut-off valve in the first intake passage is opened, and at least in the region where fuel is injected during the intake stroke, interference between the first intake valve and fuel spray is reduced, so that the intake valve is moved to the intake valve. Deposition and soot generation can be reduced.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 4 are diagrams showing a configuration of a direct in-cylinder injection spark ignition engine (hereinafter, referred to as an engine) according to a first embodiment of the present invention. First, the configuration of the engine will be described. The engine according to the present embodiment includes a combustion chamber cavity 2 having a concave portion formed on the top surface of a piston 1 and a spark plug inserted into a cylinder head of a cylinder 17 facing the combustion chamber cavity 2. 4 and a high-pressure fuel injection valve 6 below the intake port 5 for directly injecting fuel into the cylinder obliquely downward with respect to the combustion chamber 3. In the present embodiment, three intake valves 7 and intake ports 5 are formed for one cylinder, but the first intake valve 7a located at the center of the three intake valves 7
As shown in FIG. 3, the first intake port 5a connected to the first intake port 5a receives the intake air flowing through the first intake port 5a.
The intake port shape is directed toward the inside of the combustion chamber cavity 2 on the top surface. A shutoff valve 12 is provided in the first intake passage 10a upstream of the first intake port 5a.
An evaporative purge outlet 14 is provided downstream of 2. Also,
The second intake port 5b and the third intake port connected to the two second intake valves 7b and the third intake valve 7c on both sides of the first intake valve 7a.
The intake port 5c has an intake port shape such that the intake air flowing through the intake port forms a forward tumble gas flow 19 in the combustion chamber 3 as shown in FIG. A variable valve mechanism 16 and a shutoff valve opening / closing mechanism 13 are provided to open and close the first intake valve 7a, the second intake valve 7b, and the third intake valve 7c, respectively, according to the operating conditions of the engine. In addition, 8 is an exhaust valve, 10b is a second intake passage connected to the second intake port 5b, 10c is a third intake passage connected to the third intake port 5c, 11 is a collector, and 15 is an evaporative purge control mechanism.

The operating state and load of the engine are detected by an accelerator opening sensor 22 and the number of revolutions is detected by a crank angle sensor 21.
8 is input. The control unit 18 controls the shut-off valve opening / closing mechanism 13 and the variable valve mechanism 16 according to the operating state of the engine, as described later, and also functions as a fuel injection timing control means, and is adapted to the operating state. The high-pressure fuel injection valve 6 is driven according to the injection timing.

As for the shape of the intake port, the first intake port 5a is directed up into the combustion chamber cavity 2 on the top surface of the piston 1, so that the first intake port 5a stands upright with respect to the cylinder 17 near the first intake valve 7a. The third intake ports 5b, 5c
In order to form the forward tumble gas flow 19, a straight shape is formed near the second and third intake valves 7b and 7c. In addition,
FIG. 6 shows an example of the variable valve mechanism 16 used in the present embodiment.

Next, the operation of the present embodiment will be described. In the stratified combustion region where the operating conditions of the engine are low, medium speed, and low load,
As shown in FIG. 7, the third intake valve 7 is controlled by the variable valve mechanism 16.
c is stopped, only the first intake valve 7a and the second intake valve 7b are lifted, and the shutoff valve 12 in the first intake passage 10a is closed by the shutoff valve opening / closing mechanism 13, so that the gas flow in the cylinder is reduced. And the second intake port 5b
The intake air entering the combustion chamber 3 via the intake valve 7b is
A strong swirl flow 9 that moves from the direction of the second intake valve 7b to the direction of the exhaust valve 8 and further rotates toward the third intake valve 7c.
By injecting the fuel at least in the latter half of the compression stroke, the swirl flow 9 stratifies the fuel around the spark plug 4 and operates at an ultra-lean air-fuel ratio to improve fuel efficiency, and the fuel is ignited. Since the fuel does not go directly to the plug 4 but goes to the spark plug 4 through the combustion chamber cavity 2 on the surface of the piston 1 once, the atomization and vaporization of the fuel proceeds, and there is no misfire due to the adhesion of the liquid fuel to the spark plug 4, You will be able to drive stably.

In the weak stratified combustion region where the operating condition of the engine is in a low to medium speed / medium load region, as shown in FIG.
As a result, the first intake valve 7a, the second intake valve 7b, and the third intake valve 7c are lifted, and the shutoff valve 12 in the first intake passage 10a is closed by the shutoff valve opening / closing mechanism 13.
The gas flow in the cylinder is slightly weakened, and the intake air entering the combustion chamber 3 from the second intake port 5b via the second intake valve 7b and the combustion chamber from the third intake port 5c via the third intake valve 7c. 3 generates two forward tumble gas flows 19, and injects fuel at least in the first half of the compression stroke, whereby the two forward tumble gas flows 1
A weak stratification that creates a zone of fuel mixture in the middle of 9
Drive at a lean air-fuel ratio to improve fuel efficiency.

As shown in FIG. 8, when the operating condition of the engine is in a homogeneous lean burn region in a low / medium speed / medium load region, the third intake valve 7c is stopped by the variable valve mechanism 16, and the first intake valve 7a is stopped. By lifting only the second intake valve 7b and opening the shutoff valve 12 in the first intake passage 10a by the shutoff valve opening / closing mechanism 13, the second intake valve 7 is moved from the second intake port 5b.
b, a strong swirl flow 9 that is generated by intake air entering the combustion chamber 3 from the second intake valve 7b toward the exhaust valve 8 and further rotates toward the third intake valve 7c. The fuel is weakened by the flow of intake air entering the combustion chamber 3 from the first intake port 5a via the first intake valve 7a, and the fuel is injected at least in the intake stroke to achieve a homogenized fuel mixture and a lean air-fuel ratio. To improve fuel efficiency.

Further, in the homogeneous combustion region where the operating condition of the engine is a high speed / high load region, the first intake valve 7a and the second intake valve 7b are lifted by the variable valve mechanism 16 as shown in FIG. , The first intake passage 10 by the shut-off valve opening / closing mechanism 13.
By opening the shut-off valve 12 in a, the intake port area is increased and the charging efficiency is improved, and the fuel is injected at least during the intake stroke to create a homogeneous air-fuel mixture as a whole in the cylinder, and the output area also increases. Sufficient performance can be secured.

In the case of purging the evaporative fuel, as shown in FIG. 10, in the present embodiment, the evaporative fuel is directly combusted on the top surface of the piston 1 from the first intake port 5a via the first intake valve 7a. Since the fuel is introduced into the chamber cavity 2, even when the engine is operated under the condition that the evaporative fuel is purged at the time of stratified combustion in a low speed / low load range, the swirl flow 9
The purge gas concentrates in the combustion chamber cavity 2 on the top surface of the piston 1 at the center of the combustion chamber and mixes with the injected fuel in the combustion chamber cavity 2 to enable stable combustion and the exhaust performance is not deteriorated.

Also, when the operating conditions of the engine are such that the evaporative fuel is purged during weakly stratified combustion in a low-medium-speed / medium-load region, as shown in FIG. The fuel concentrates and mixes with the fuel mixture zone in the middle of the gas flow, enabling stable combustion.

When the engine is operated under the condition of homogeneous lean combustion in the low-medium-speed / medium-load region and the homogeneous combustion in the high-speed / high-load region, the evaporative fuel is purged as shown in FIGS. In addition, since the fuel injection is performed during the intake stroke, the purge gas and the injected fuel are sufficiently mixed, and stable combustion can be performed similarly to the conventional intake port fuel injection engine.

Further, when the operating conditions of the engine are stratified combustion in a low speed / low load range and weak stratified combustion in a low / medium speed / medium load range, the intake port negative pressure decreases due to a large throttle valve opening. Although the purge flow rate of the evaporative fuel to the intake port decreases, according to the present embodiment, the evaporative fuel is introduced into the first intake port 5a downstream of the shutoff valve 12 when the shutoff valve 12 is closed. Since the intake port negative pressure develops, an effect that the purge flow rate does not decrease is also obtained. FIG. 1 shows an example of an operation region in which each combustion described above is performed.
It is shown in FIG.

FIGS. 15 to 17 show a second embodiment. The second embodiment is different from the first embodiment in that
As a sectional shape of the first intake port 5a toward the combustion chamber cavity 2 on the top surface of the piston 1, a guide 20 for guiding intake air flow is provided above the intake port 5a. FIG.
FIG. 8 shows an example of another guide shape.

According to the second embodiment, in addition to the operation and effect of the first embodiment, as shown in FIG. 19, the operating conditions of the engine are changed to a stratified combustion region in a low / medium speed / low load region and a low / middle When purging the evaporative fuel in the weakly stratified combustion region in the high speed / medium load region, the evaporative fuel flows through the upper portion of the first intake port 5a, and mainly the piston directly from the opening of the first intake valve 7a on the exhaust valve 8 side. The purge gas is more concentrated in the combustion chamber cavity 2 on the top surface of the piston 1 in the middle of the swirl flow 9 or two forward tumble gas flows 19 to enter the combustion chamber cavity 2 on one top surface, Mixing with the injected fuel in the combustion chamber cavity 2 enables stable combustion.

FIG. 20 shows a third embodiment. In the third embodiment, the lift amount of the first intake valve 7a is set to be larger than the lift amounts of the second intake valve 7b and the third intake valve 7c in the first embodiment. It is shortened.

According to the third embodiment, the operating condition of the engine is set such that the third intake valve 7c is stopped by the variable valve mechanism 16 in the homogeneous lean burn region in the low-medium-speed / medium-load region, and the first intake valve is stopped. Only the valve 7a and the second intake valve 7b are lifted, and the shutoff valve 12 in the first intake passage 10a is opened by the shutoff valve opening / closing mechanism 13, so that the fuel is injected at least in the intake stroke, and the high speed / high load area. The first intake valve 7a, the second intake valve 7b, and the third intake valve 7b are controlled by the variable valve mechanism 16 in the homogeneous combustion region.
The intake valve 7c is lifted, and the shut-off valve 12 in the first intake passage 10a is opened by the shut-off valve opening / closing mechanism 13, and at least in a region where fuel is injected at the time of the intake stroke, the first intake valve 7a and the fuel spray Since the interference is reduced, the deposit on the intake valve 7 and the occurrence of soot can be reduced.

[0027]

As described above, in the direct in-cylinder injection spark ignition engine according to the first aspect, a strong swirl flow is formed during stratification by controlling the opening and closing of each port according to the operating conditions. And formation of two forward tumble gas flows during weak stratification, formation of weak swirl flow during homogeneous lean burn,
Achieving both low intake resistance in the output range under high load, improving fuel efficiency by ultra-lean air-fuel ratio operation by fuel injection at a specific time, and improving output performance by increasing air filling efficiency during throttle fully open operation There is an effect that can be achieved. Also, when evaporating fuel is purged during stratification,
Since the gas can be introduced from the central port and the gas flow in the combustion chamber can be controlled, the purge gas can be concentrated in the combustion chamber on the top surface of the piston, mixing with the injected fuel can be promoted in this combustion chamber, and combustion is improved. Thus, there is an effect that deterioration of exhaust performance can be prevented.

In the direct in-cylinder injection spark ignition engine according to the second aspect of the present invention, the operating condition of the engine is such that in a stratified combustion region in a low-medium-speed, low-load region, the gas flow in the cylinder is enhanced and
By forming a strong swirl flow and injecting fuel at least in the latter stage of the compression stroke, stratification of the fuel around the spark plug is attempted, driving at ultra-lean air-fuel ratio to improve fuel efficiency, and fuel Through the surface combustion chamber,
Since the fuel goes toward the spark plug, atomization and vaporization of the fuel progress, and there is no misfire due to liquid fuel adhesion to the spark plug.
This has the effect of allowing stable operation. In addition, even when purging the evaporative fuel, the evaporative fuel is directly introduced from the central first intake port into the combustion chamber on the piston top surface, so that the purge gas enters the combustion chamber on the piston top surface, which is the center of the swirl gas flow. There is an effect that the fuel is concentrated and mixed with the injected fuel in the combustion chamber, thereby enabling stable combustion.

[0029] In the direct in-cylinder injection spark ignition engine according to the third aspect, in the stratified combustion region in the low-medium-speed / medium-load region, the operating condition of the engine slightly weakens the gas flow in the cylinder. The intake air entering the combustion chamber creates two forward tumble flow gas flows and injects fuel at least during the first half of the compression stroke, thereby creating a fuel mixture band intermediate the two tumble flow gas flows. There is an effect that it is possible to perform weak stratification, operate at a lean air-fuel ratio, and improve fuel efficiency. Also, when purging the evaporative fuel, the purge gas concentrates at the center of the two forward tumble flow gas flows, and has the effect of mixing with the fuel mixture zone in the middle of the gas flows and enabling stable combustion.

In the direct in-cylinder injection spark ignition engine according to the fourth aspect, in the engine operating condition, in a homogeneous lean burn region in a low-medium-speed / medium-load region, a strong swirl flow is applied to the central first intake air. Attenuated by the flow of intake air entering the combustion chamber flowing from the port, the fuel is injected at least during the intake stroke to achieve a homogenized fuel mixture and operate at a lean air-fuel ratio,
There is an effect that fuel efficiency can be improved. Further, when purging the evaporative fuel, since the fuel injection is performed during the intake stroke, the purge gas and the injected fuel are sufficiently mixed, and there is an effect that stable combustion can be performed similarly to the conventional intake port fuel injection engine.

In the direct in-cylinder injection spark ignition engine according to the fifth aspect of the present invention, the operating condition of the engine is to increase the intake port area and improve the charging efficiency in a homogeneous combustion region in a high speed and high load region. By injecting the fuel at least during the intake stroke, the air-fuel mixture is homogenized, and there is an effect that sufficient performance can be secured in the output region. Further, when evaporating fuel is purged, since the fuel injection is performed during the intake stroke, the purge gas and the injected fuel are sufficiently mixed, and there is an effect that stable combustion can be performed similarly to the conventional intake port fuel injection engine.

In the direct in-cylinder injection spark ignition engine according to the sixth aspect, the flow flowing from the central first intake port flows into the combustion chamber on the piston top surface, and flows from the second and third intake ports. In order to form a forward tumble flow, the required gas flow (the formation of a strong swirl flow during stratification and the two forward tumble gas flows during weak stratification) during the opening / closing control of each port according to the operating conditions , Weak swirl flow during homogeneous lean burn, and low intake resistance in the output region at high rotation and high load).

In the direct in-cylinder injection spark ignition engine according to the seventh aspect, the operating conditions of the engine are a stratified combustion region in a low / medium speed / low load region and a weak stratification in a low / medium speed / medium load region. When purging the evaporative fuel in the combustion area, the evaporative fuel flows in the upper part of the central first intake port and mostly enters the combustion chamber on the top surface of the piston directly from the exhaust valve side opening of the first intake valve. Is more concentrated in the combustion chamber on the piston top surface located at the center of the swirl gas flow or the two forward tumble flow gas flows, so that mixing with the injected fuel is promoted in this combustion chamber, and stable combustion is possible. effective.

[0034] In the direct in-cylinder injection spark ignition engine according to claim 8, the operating condition of the engine is such that the third intake valve is deactivated in a homogeneous lean burn region in a low-medium-speed / medium-load region, Only the first intake valve and the second intake valve are operated, and the shut-off valve in the first intake passage is opened, and the first intake in a region where fuel is injected at least in an intake stroke and a homogeneous combustion region in a high speed / high load region. The valve, the second intake valve, and the third intake valve are operated, and the shutoff valve in the first intake passage is opened, and interference between the first intake valve and fuel spray is reduced at least in a region where fuel is injected at least during an intake stroke. Therefore, there is an effect that deposition of soot on the intake valve and generation of soot can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a direct in-cylinder injection spark ignition engine according to Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating a configuration of a direct in-cylinder injection spark ignition engine according to the first embodiment;

FIG. 3 is a sectional view taken along line S3-S3 of FIG. 2;

FIG. 4 is a sectional view taken along line S4-S4 of FIG. 2;

FIG. 5 is a diagram illustrating the operation of the first embodiment.

FIG. 6 is a diagram illustrating an example of a variable valve mechanism 16 according to the first embodiment.

FIG. 7 is a diagram illustrating the operation of the first embodiment.

FIG. 8 is a diagram illustrating the operation of the first embodiment.

FIG. 9 is a diagram illustrating the operation of the first embodiment.

FIG. 10 is a diagram illustrating the operation of the first embodiment.

FIG. 11 is a diagram illustrating the operation of the first embodiment.

FIG. 12 is a diagram illustrating the operation of the first embodiment.

FIG. 13 is a diagram illustrating the operation of the first embodiment.

FIG. 14 is a diagram showing an example of an operation region in which each combustion is performed.

FIG. 15 is a diagram showing a configuration of a second embodiment.

16 is a sectional view taken along S16-S16 of FIG.

FIG. 17 is a sectional view taken along line S17-S17 of FIG. 16;

FIG. 18 is a diagram showing an example of another guide shape.

FIG. 19 is a diagram illustrating the operation of the second embodiment.

FIG. 20 is a diagram illustrating Embodiment 3;

FIG. 21 is a longitudinal sectional view showing a conventional direct in-cylinder injection spark ignition engine.

FIG. 22 is a cross-sectional view showing a conventional direct in-cylinder injection spark ignition engine.

FIG. 23 is a diagram showing a system configuration of a conventional direct in-cylinder injection spark ignition engine.

[Explanation of symbols]

 Reference Signs List 1 piston 2 combustion chamber cavity 3 combustion chamber 4 spark plug 5 intake port 5a first intake port 5b second intake port 5c third intake port 6 high-pressure fuel injection valve 7 intake valve 7a first intake valve 7b second intake valve 7c 3 intake valve 8 exhaust valve 9 swirl flow 10a first intake passage 10b second intake passage 10c third intake passage 11 collector 12 shutoff valve 13 shutoff valve opening / closing mechanism 14 evaporative purge outlet 15 evaporative purge control mechanism 16 variable valve mechanism 17 cylinder 18 Control unit 19 Forward tumble gas flow 20 Guide 21 Crank angle sensor 22 Accelerator opening sensor

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02B 23/08 F02B 23/08 Q 23/10 23/10 Z 31/00 31/00 Z 31/02 31/02 L F02D 13/02 F02D 13/02 E HG F02M 25/08 F02M 25/08 P

Claims (8)

[Claims] 1. A combustion chamber having a recess formed on a top surface of a piston, an ignition plug provided facing the combustion chamber, and fuel being directly injected into a cylinder obliquely downward from an intake port side of the combustion chamber. In the direct-injection type spark ignition engine having an injection valve, three intake ports are formed for one cylinder, and a flow of intake air flows through a central first intake port located at the center of the three intake ports. Formed in a shape directly facing the recess of the piston, and provided with a shutoff valve on the upstream side of the central first intake port,
An outlet for the evaporative purge is provided at the central first intake port downstream of the shut-off valve, and the second exhaust ports located on both sides of the central first intake port are provided.
A variable valve mechanism configured to form the intake port and the third intake port into a shape in which the flow of intake air generates a tumble flow in the combustion chamber, and stop the operation of an intake valve that opens and closes the third intake port according to an operation state; Direct in-cylinder comprising: a shut-off valve opening / closing mechanism that controls the opening / closing of a shut-off valve according to the operating state of the engine; and an injection timing control unit that controls the fuel injection timing according to the operating state of the engine. Injection spark ignition engine. 2. The variable valve mechanism stops the operation of the intake valve of the third intake port when the operation state of the engine is in a region where the stratified combustion for collecting the air-fuel mixture is performed in the vicinity of the ignition plug, and the shut-off valve opening / closing mechanism operates. 2. The direct in-cylinder injection spark ignition engine according to claim 1, wherein the shut-off valve of the central first intake port is closed, and the injection timing control means sets the fuel injection timing to the latter half of the compression stroke. 3. The variable valve mechanism activates an intake valve of a third intake port, and the shut-off valve opening / closing mechanism operates when the engine is in an operation state where weak stratified combustion for collecting an air-fuel mixture is performed near an ignition plug. 3. The direct in-cylinder injection spark ignition engine according to claim 1, wherein the shut-off valve of the first intake port is closed, and the injection timing control means sets the fuel injection timing in the first half of the compression stroke. 4. When the operating state of the engine is in a region for performing a homogeneous lean combustion in which a homogeneous lean mixture is formed in the combustion chamber,
The variable valve mechanism stops the intake valve of the third intake port, the shutoff valve opening and closing mechanism opens the shutoff valve of the central first intake port, and the injection timing control means sets the fuel injection timing to the intake stroke.
The direct in-cylinder injection spark ignition engine according to claim 1, wherein 5. The variable valve mechanism activates an intake valve of a third intake port when the operating state of the engine is in a region where homogeneous combustion is performed to form a homogeneous air-fuel mixture in the combustion chamber, and the shut-off valve opening / closing mechanism operates. 5. The direct in-cylinder injection spark ignition engine according to claim 1, wherein the shut-off valve of the central first port is opened, and the injection timing control means sets the fuel injection timing to the intake stroke. 6. The central first intake port has a shape that stands upright with respect to the cylinder and points toward the recess of the piston, and the second intake port and the third intake port have a straight shape that generates a tumble flow in the combustion chamber. The direct in-cylinder injection spark ignition engine according to any one of claims 1 to 5, characterized in that: 7. A guide groove formed in the upper wall of the central first intake port along the flow direction of the intake air, and the outlet of the evaporative purge is opened near the guide groove.
7. A direct in-cylinder injection spark ignition engine according to any one of claims 6 to 6. 8. A lift amount of an intake valve that opens and closes a central first intake port is set smaller than an intake valve that opens and closes another second intake port or a third intake port. A direct in-cylinder injection spark ignition engine according to any one of claims 6 to 7.