JPH108967A - Direct cylinder injection type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make stable operation capable in a strong stratification region and a uniform region also make stable combustion capable even in a weak stratification region intermediate between the stratification region and the uniform region, in a direct cylinder injection spark ignition engine. SOLUTION: A spark ignition engine is constituted so as to have a combustion chamber 2 having a recessed part formed in a top surface of a piston 1, spark plug 4 inserted in the vicinity of a side wall of combustion chamber and a high pressure fuel injection valve formed so as to directly inject fuel into a cylinder diagonally in a downward direction relating to a combustion chamber 3 in a lower part of an intake port. Here, three intake valves and intake ports are formed in a single cylinder, a central first port part connected to a first intake valve 7a is formed in a port shape such as forming a regular tumble flow in the combustion chamber by an intake flow flowing in through this port, a variable tappet valve mechanism, open/close controlling the first/ second intake valves 7a, 7b by an operating condition, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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, there is one as shown in FIG. 8 (Japanese Patent Application Laid-Open No. 4-112931). The direct in-cylinder injection spark ignition engine disclosed herein is inserted into a concave combustion chamber 2 formed on the top surface of a piston 1 and near the wall of the combustion chamber 3 at the time of ignition as the piston 1 rises. Spark plug 4 and intake port 5
In the lower part, a high-pressure fuel injection valve 6 obliquely downward with respect to the combustion chamber 3
The fuel injection is performed at least when the engine is in a specific engine operating state, stratification of the fuel is performed, and operation is performed at an ultra-lean air-fuel ratio to improve fuel efficiency. However, this injection valve 6,
In the case of the positional relationship of the ignition plug 4, in the intake port shape of a general engine, the intake air entering the combustion chamber 3 from the intake port 5 via the intake valve passes through the upper surface of the combustion chamber from the intake side to the exhaust side and downward. Then, a tumble flow 9 is formed in the forward direction such that it rotates in the direction of the piston and further along the surface of the piston 1 in the direction of the intake valve. There is a problem that misfire is likely to occur due to the adhesion of the liquid fuel to the plug 4.

As a countermeasure for this, there is a countermeasure as shown in FIG. 9 (Japanese Patent Laid-Open No. 6-146886). This is due to the concave combustion chamber 2 formed on the top surface of the piston 1.
A spark plug 4 inserted near the side wall of the combustion chamber 3 at the time of ignition as the piston 1 rises, and a high-pressure fuel injection valve 6 installed obliquely downward with respect to the combustion chamber 3 below the intake port 5. In the direct cylinder injection type spark ignition engine, the head is designed so that the intake port 5 is upright.
The intake air that enters the combustion chamber 3 from the port 5 via the intake valve 7 is first guided downward in the direction of the piston, then follows the surface of the piston 1 and rises in the direction of the exhaust valve, and moves upward in the direction of the exhaust valve. This is to form a tumble flow 10 in the opposite direction to that described above, which rotates from the exhaust side to the intake side. Therefore, the fuel does not directly go to the spark plug 4 direction by the above-described tumble flow gas flow 10 but goes to the spark plug once through the surface of the piston 1, so that the fuel atomization and vaporization progress, and the spark plug No misfire due to adhesion of the liquid fuel to the fuel cell 4 can be achieved, and stable operation can be achieved.

[0004]

However, in such a conventional direct in-cylinder injection type spark ignition engine, in order to form a tumble flow in the opposite direction, a head design in which the intake ports are arranged in series is adopted. As a result, the overall height of the engine is increased, and a configuration is required to respond to the new engine, resulting in a problem that the cost is greatly increased.
In this specification, stable operation is possible in a strong stratified zone and a homogeneous zone, but stable combustion is difficult in a weak stratified zone between a stratified zone and a homogeneous zone.

The present invention has been made in view of such a conventional problem. Three intake valves and three intake ports are formed in one cylinder, and a central intake port among them has a reverse tumble flow gas flow. The other two intake ports are shaped to create forward tumble flow gas flow, and the ports that create forward and reverse tumble flow gas flow are varied in intake valve lift using a variable valve mechanism according to operating conditions. It is intended to solve the above-mentioned problem by opening and closing.

[0006]

According to the present invention, there is provided a combustion chamber having a recess formed in a top surface of a piston, a spark plug inserted near a side wall of the combustion chamber, and an intake air. In a direct cylinder injection type spark ignition engine having a high pressure fuel injection valve in which a fuel is directly injected into a cylinder obliquely downward with respect to a combustion chamber below a port, one cylinder has three intake valves and one intake port. And a central first port portion connected to the first intake valve has a port shape such that an intake flow flowing through the port forms a reverse tumble flow in the combustion chamber. The second port portion connected to the second intake valve has a port shape such that an intake flow flowing through the port forms a forward tumble flow in the combustion chamber, and the first and second intake valves are operated by the engine. Open / close control according to conditions A structure in which a variable valve mechanism.

Further, in the present invention, when the operating condition of the engine is in a stratified combustion region in a low-medium-speed, low-load region, the second valve-operating mechanism uses a variable valve mechanism.
The intake valve is stopped, only the first intake valve is lifted, and the fuel injection timing is set in the latter stage of the compression stroke. When the operating condition of the engine is in a low stratified combustion region in a low / medium speed / medium load region, the first intake valve is stopped. Only the second intake valve is lifted, and the fuel injection timing is set in the first half of the compression stroke. On the other hand, in the homogeneous combustion region where the engine operating condition is a high speed / high load region, the first intake valve and the second intake valve are controlled by the variable valve mechanism. Both are lifted, and the fuel injection timing is set during the intake stroke.

Further, the present invention provides a port shape for forming a forward tumbling and a reverse tumbling, wherein a central first port portion has a shape standing upright with respect to a cylinder near a first intake valve in order to form a reverse tumbling, The part is formed straight near the intake valve to form a forward tumble.

Further, according to the present invention, a deep cavity for reverse tumbling is provided at the center of a symmetrical line in the direction of the intake and exhaust valves on the piston crown surface as a piston shape for enhancing gas flow in each of forward tumbling and reverse tumbling. And shallow cavities for forward tumbling are provided on both sides thereof.

Further, in the present invention, the lift amount of the first intake valve is shorter than the lift amount of the second intake valve in the lift amounts of the three intake valves.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, the same parts and members as those described in the related art will be described using the same reference numerals.

(First Embodiment) FIGS. 1 and 2 are views showing a first embodiment of the present invention. First, the configuration of a direct in-cylinder injection spark ignition engine according to a first embodiment will be described. A combustion chamber 2 having a recess formed on the top surface of a piston 1 and an ignition inserted near a side wall of the combustion chamber Plug 4
In a direct cylinder injection type spark ignition engine having a high pressure fuel injection valve 6 below the intake port 5a for directly injecting fuel obliquely downward with respect to the combustion chamber 3 into the cylinder, one cylinder Three intake valves 7a, 7b and intake ports 5a, 5b
And a central first port portion 5a connected to the first intake valve 7a has a port shape such that an intake flow flowing through the port forms a reverse tumble flow 10 in the combustion chamber 3. The second port portion 5b connected to the two second intake valves 7b on both sides of the valve 7a has a port shape such that an intake flow flowing through the port forms a forward tumble flow 9 in the combustion chamber 3. . Then, the first intake valve 7a,
A variable valve mechanism 11 for controlling the opening and closing of the second intake valve 7b according to operating conditions of the engine is provided.

As for the port shape for forming the forward tumbling and the reverse tumbling, the central first port portion 5a is formed so as to be upright with respect to the cylinder 13 near the first intake valve 7a in order to form the reverse tumbling. The portion 5b has a straight shape near the second intake valve 7b in order to form a forward tumble.

Next, the operation will be described.

In the stratified combustion region where the operating condition of the engine is a low-medium-speed, low-load region, as shown in FIG.
As a result, the second intake valve 7b stops, only the first intake valve 7a is lifted, and the gas flow in the cylinder is strengthened. The intake air entering the combustion chamber 3 from the central first port portion 5a via the first intake valve 7a is first guided downward in the direction of the piston. Subsequently, it follows the surface of the piston 1 and rises in the direction of the exhaust valve.
A reverse tumble flow 9 is formed such that the upper surface of the combustion chamber 3 rotates from the exhaust side to the intake side, and the fuel is injected late in the compression stroke. The fuel is stratified and operated at an ultra-lean air-fuel ratio to improve fuel efficiency, and the fuel does not directly go to the spark plug 4 but goes to the plug once through the surface of the piston 1. As a result, the atomization and vaporization of the fuel progress, and there is no misfire due to the adhesion of the liquid fuel to the ignition plug 4, so that stable operation can be achieved.

In the weak stratified combustion region where the engine is operating in a low-medium-speed / medium-load region, as shown in FIG.
Due to 1, the first intake valve 7a is stopped and only the second intake valve 7b is lifted to increase the gas flow in the cylinder. The intake air entering the combustion chamber 3 from the two second port portions 5b via the second intake valves 7b goes down the upper surface of the combustion chamber 3 from the intake side to the exhaust side, and descends in the piston direction. Subsequently, two forward tumble flows 10 are formed along the surface of the piston 1 so as to rotate from the exhaust side to the intake side, and the fuel is injected in the first half of the compression stroke, so that the two forward tumble flows 10 Weak stratification to generate a band of fuel mixture in the middle and operation at 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 and high-load region, as shown in FIG. 5, both the first intake valve 7a and the second intake valve 7b are lifted by the variable valve mechanism 11, By increasing the area and injecting the fuel at least during the intake stroke, a homogeneous air-fuel mixture is created, and sufficient performance can be ensured in the output region.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG. The direct in-cylinder injection spark ignition engine according to the second embodiment has a concave combustion chamber 2 formed on the top surface of a piston 1 and a vicinity of a side wall of a combustion chamber 3 at the time of ignition as the piston 1 rises. Spark plug 4 to be inserted
In a direct cylinder injection type spark ignition engine in which a high-pressure fuel injection valve 6 is installed obliquely downward with respect to the combustion chamber 3 below the intake port 5a, three intake valves 7a, 7b and an intake port are provided for one cylinder. The central first port portion 5a, which forms 5a and 5b and is connected to the first intake valve 7a, has a port shape such that the intake air flowing through the port forms a reverse tumble flow 9 in the combustion chamber 3. . The second port portion 5b connected to the two second intake valves 7b on both sides of the first intake valve 7a has a port in which the intake air flowing through the port forms a forward tumble flow 10 in the combustion chamber 3. Shape. In the first embodiment, the variable valve mechanism 11 for controlling the opening and closing of the first intake valve 7a and the second intake valve 7b according to the operating conditions of the engine is provided. In order to enhance the gas flow, a deep cavity 14 for reverse tumbling is provided at the center of the symmetry line 16 in the direction of the intake and exhaust valves on the piston crown surface, and shallow cavities 15 for forward tumble are provided on both sides thereof.

As a result, the operating condition of the engine is
The first operation is performed by the variable valve mechanism 11 in the stratified combustion region in a low load region.
In a region where the intake valve 7a is stopped and only the second intake valve 7b is lifted, the intake air entering the combustion chamber 3 from the central first port portion 5a via the first intake valve 7a draws and exhausts the piston 1 crown surface. At the center of the symmetry line 16 in the valve direction, a deep cavity 14 for counter-tumbling is rotated in the counter-tumbling direction in the cavity, and the fuel is injected late in the compression stroke so that the fuel flows through the counter-tumble gas flow 9. Once through the piston surface, the fuel goes to the plug, so that the fuel does not go directly to the spark plug, the fuel atomization and vaporization progress, and there is no misfire due to the adhesion of the liquid fuel to the spark plug 4 and the air-fuel mixture around the spark plug Can be concentrated, so that stable driving can be achieved.

In an engine operating condition in a low stratified combustion region in a low / medium speed / medium load region, the variable intake valve mechanism 11 stops the first intake valve 7a and in a region where only the second intake valve 7b lifts, The gas flow inside the combustion chamber 3 enters the combustion chamber 3 from the two second ports 5b through the second intake valve 7b, and the forward tumble flow 10 is formed by the shallow cavity 15 into a symmetrical line 16 of the piston crown surface in the direction of the intake and exhaust valves. By forming the two in between and injecting the fuel in the middle of the tumble flow in the first half of the compression stroke, a weak stratification is generated in the middle of the two forward tumble flow gas flows 10 to form a band of the fuel mixture. The operation is performed at 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 and high-load region, both the first intake valve 7a and the second intake valve 7b are lifted by the variable valve mechanism 11 to increase the port area and increase the fuel area. By injecting at least at the time of the intake stroke, a homogeneous air-fuel mixture is produced, and sufficient performance can be ensured in the output region.

(Third Embodiment) Next, a third embodiment will be described with reference to FIG.

The direct in-cylinder injection spark ignition engine according to the third embodiment includes a combustion chamber 2 having a recess formed on the top surface of a piston 1, an ignition plug 4 inserted near the side wall of the combustion chamber. In a direct cylinder injection type spark ignition engine having a high pressure fuel injection valve 6 for directly injecting fuel obliquely downward with respect to the combustion chamber 3 into the cylinder below the intake port 5a, three cylinders per cylinder Intake valves 7a, 7b and intake ports 5a, 5
b, and the central first port portion 5a connected to the first intake valve 7a has a port shape such that the intake air flowing through the port forms the reverse tumble flow 9 in the combustion chamber 3. Two second intake valves 7b on both sides of the first intake valve 7a
The second port portion 5b connected to the port has a port shape such that the intake flow flowing through the port forms a forward tumble flow 10 in the combustion chamber 3. In the first embodiment described above, in which the variable valve mechanism 11 for controlling the opening and closing of the first intake valve 7a and the second intake valve 7b according to the operating conditions of the engine is provided, the lift amounts of the three intake valves 7a and 7b are set. , The lift amount 17a of the first intake valve 7a is
Is smaller than the lift amount 17b. Thus, the operating condition of the engine is such that the first intake valve 7a and the second intake valve 7b are both lifted by the variable valve mechanism 11 in the homogeneous combustion region in the high speed / high load region, and the fuel is injected at least during the intake stroke. In this case, the interference between the first intake valve 7a and the fuel spray is reduced, so that the deposit on the intake valve and the occurrence of soot can be reduced.

[0024]

As described above, according to the present invention, the structure of the combustion chamber having the recess formed on the top surface of the piston, the spark plug inserted near the wall of the combustion chamber, In a direct cylinder injection type spark ignition engine having a high pressure fuel injection valve in which a fuel is directly injected into a cylinder obliquely downward with respect to a combustion chamber at a lower portion of an intake port, three intake valves per cylinder and intake air are provided. A central first port portion which forms a port and is connected to the first intake valve has a port shape such that an intake flow flowing through the port forms a reverse tumble flow in the combustion chamber. The second port portion connected to the two second intake valves has a port shape such that the intake flow flowing through the ports forms a forward tumble flow in the combustion chamber. A variable valve mechanism for controlling the opening and closing of the first and second intake valves according to the operating conditions of the engine is provided. When the operating conditions of the engine are in a stratified combustion region in a low-medium-speed, low-load region, the variable valve mechanism is used. The second intake valve is stopped and only the first intake valve is lifted to increase the gas flow in the cylinder, and the intake air entering the combustion chamber from the central first port portion via the first intake valve is first directed downward. It is guided in the direction of the piston, then moves along the piston surface, rises in the direction of the exhaust valve, and forms a reverse tumble flow that rotates the upper surface of the combustion chamber from the exhaust side to the intake side. By injecting, the surroundings of the fuel ignition plug are stratified by the reverse tumble flow gas flow, driving at an ultra-lean air-fuel ratio and improving fuel efficiency,
And the fuel does not go directly to the spark plug, but goes to the plug once through the piston surface.
In addition, vaporization proceeds, and there is no misfire due to adhesion of liquid fuel to the ignition plug, and stable operation can be performed. When the operating condition of the engine is a weak stratified combustion region in a low-medium-speed / medium-load region, the first intake valve is stopped by the variable valve operating mechanism, and only the second intake valve is lifted, thereby increasing the gas flow in the cylinder, and The intake air that enters the combustion chamber from the two second ports through the second intake valve goes from the intake side to the exhaust side on the upper surface of the combustion chamber, descends toward the piston, and then descends along the piston surface toward the exhaust side. Weak stratification that forms two forward tumble flows that rotate from the air to the intake side and injects fuel in the first half of the compression stroke creates a zone of fuel mixture in the middle of the two forward tumble flow gas flows And operate at a lean air-fuel ratio to improve fuel efficiency. Furthermore, in the homogeneous combustion region where the operating condition of the engine is a high-speed and high-load region, both the first intake valve and the second intake valve are lifted by a variable valve mechanism to increase the port area and to inject fuel at least during the intake stroke. By doing so, a homogeneous air-fuel mixture can be created, and sufficient performance can be ensured in the output region.

Each embodiment has the following effects in addition to the above-mentioned common effects.

Since the variable valve mechanism is provided, by selecting an appropriate operating angle at low speed, medium speed and high speed with respect to the output characteristics in a high load range, in addition to the output improving characteristics of the direct injection engine, furthermore, Can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing a direct in-cylinder injection spark ignition engine according to a first embodiment of the present invention, (a) is a top view, (b) is a cross-sectional view taken along line AA in (a), (B) is a sectional view taken along line BB in (a).

FIG. 2 is a side view showing the direct in-cylinder injection spark ignition engine according to the first embodiment of the present invention.

FIG. 3 is a diagram showing the operation of the first embodiment of the present invention.

FIG. 4 is a diagram showing the operation of the first embodiment of the present invention.

FIG. 5 is a diagram showing the operation of the first embodiment of the present invention.

6A and 6B are views showing a direct in-cylinder injection spark ignition engine according to a second embodiment of the present invention, wherein FIG. 6A is a top view, FIG. 6B is a cross-sectional view taken along line CC in FIG. (C) is a sectional view taken along line DD in (a).

FIGS. 7A and 7B are explanatory views of a direct in-cylinder injection spark ignition engine according to a third embodiment of the present invention, in which FIG. 7A shows a cam profile, and FIG. It is.

FIG. 8 is a view showing a conventional direct in-cylinder injection spark ignition engine.

FIG. 9 is a diagram showing 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 reverse tumble intake port 5b forward tumble intake port 6 high-pressure fuel injection valve 7 intake valve 7a first intake valve 7b second intake valve 8 exhaust valve 9 reverse Tumble gas flow 10 Forward tumble gas flow 11 Variable valve mechanism 12 Engine control unit 13 Cylinder 14 Deep cavity for reverse tumble 15 Shallow cavity for forward tumble 16 Symmetry line in intake and exhaust valve direction 17 Working angle (cam profile) 17a First intake Valve operating angle 17b Second intake valve operating angle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F02B 23/10 F02B 23/10 D F02D 13/02 F02D 13/02 H F02F 1/42 F02F 1 / 42 F 3/26 3/26 A

Claims (5)

[Claims] 1. A combustion chamber having a concave portion formed on the top surface of a piston, a spark plug inserted near a wall of the combustion chamber, and fuel directly obliquely downward to the combustion chamber below an intake port into a cylinder. In a direct in-cylinder injection spark ignition engine having a high pressure fuel injection valve adapted to inject, three intake valves and an intake port are formed in one cylinder, and
The central first port portion connected to the intake valve has a port shape such that the intake flow flowing through the port forms a reverse tumble flow in the combustion chamber, and is connected to the two second intake valves on both sides of the first intake valve. The second port portion has a port shape such that an intake flow flowing through the port forms a forward tumble flow in the combustion chamber, and controls opening and closing of the first and second intake valves according to operating conditions of the engine. A direct in-cylinder injection spark ignition engine characterized by having a variable valve mechanism. 2. In a stratified combustion region in which the operating condition of the engine is a low-medium-speed, low-load region, the second intake valve is stopped by the variable valve operating mechanism, only the first intake valve is lifted, and the fuel injection timing is changed to the latter stage of the compression stroke. The first intake valve is stopped and only the second intake valve is lifted, and the fuel injection timing is set in the first half of the compression stroke in the weak stratified combustion region where the engine operating conditions are low, medium speed, and medium load. A variable valve mechanism lifts both the first intake valve and the second intake valve and sets a fuel injection timing during an intake stroke in an engine operating condition in a homogeneous combustion region in a high speed / high load region. 2. The direct in-cylinder injection spark ignition engine according to 1. 3. A port shape for forming a forward tumbling and a reverse tumbling, wherein a central first port portion has a shape standing upright with respect to a cylinder near a first intake valve to form a reverse tumbling, and a second port portion has a forward tumbling shape. The direct in-cylinder injection spark ignition engine according to claim 1 or 2, wherein the engine is formed in a straight shape near the intake valve to form the spark plug. 4. A deep cavity for reverse tumbling is provided at the center of a symmetrical line of the piston crown surface in the direction of the intake and exhaust valves as a piston shape for enhancing gas flow in each of forward tumbling and reverse tumbling. 3. The direct in-cylinder injection spark ignition engine according to claim 1, wherein a shallow cavity for forward tumbling is provided. 5. In the lift amounts of the three intake valves, the first
3. The direct in-cylinder injection spark ignition engine according to claim 1, wherein a lift amount of the intake valve is shorter than a lift amount of the second intake valve.