JP3591141B2 - In-cylinder direct injection spark ignition internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an in-cylinder direct injection spark ignition internal combustion engine in which fuel is directly injected into a cylinder by a fuel injection valve and spark ignition is performed by a spark plug, and in particular, includes an exhaust gas recirculation device for recirculating exhaust gas to an intake system. And a direct injection type spark ignition internal combustion engine.
[0002]
[Prior art]
In a direct injection type spark ignition internal combustion engine, improvement of responsiveness can be expected because fuel is supplied directly into the combustion chamber.
In such an internal combustion engine, a vertical vortex intake flow (tumble vortex) is formed in the combustion chamber to perform lean combustion (hereinafter, lean combustion) with a fuel leaner than the stoichiometric air-fuel mixture, thereby improving fuel efficiency of the engine. Is adopted.
[0003]
Even with lean fuel, combustion (lean combustion) is possible if stratification can be achieved by forming a rich air-fuel mixture near the ignition plug at the time of ignition. In the stratification, the aforementioned tumble vortex flows into the combustion chamber. It can be realized by generating.
As a method for forming such a tumble vortex, a method has been conventionally proposed in which an intake port is made to be a high port (upright port) or its shape is changed.
[0004]
However, when the fuel consumption is reduced by lean combustion, nitrogen oxides (NOx) contained in exhaust gas cannot be reduced so much.
Therefore, it is effective to add an exhaust gas recirculation (hereinafter, EGR) device that recirculates the exhaust gas to the intake system to reduce the NOx by reburning the exhaust gas.
The in-cylinder direct injection spark ignition internal combustion engine has a feature that it is strong against the EGR system, can supply a large amount of EGR gas, and has a large NOx reduction effect.
[0005]
Conventionally, as a structure of a direct injection type spark ignition internal combustion engine equipped with such an EGR device, there is one shown in FIGS. 10 and 11 (see Japanese Patent Application Laid-Open No. 6-147022).
That is, in this device, a combustion chamber 42 is formed between the crown surface of the piston 40 and the lower surface of the cylinder head 41, and the intake air is supplied to one side of the cylinder head 41 across a plane including the cylinder axis along the center of the cylinder 43. A port 44 and an exhaust port 45 are provided on the other side, respectively. Each of the ports 44 and 45 is connected to the combustion chamber 42 via an intake valve 46 and an exhaust valve 47, respectively.
[0006]
A fuel injection valve 48 is mounted on a side wall of the cylinder head 41 on the side of the intake port 44, and a tip injection hole 48 a of the fuel injection valve 48 faces the inside of the combustion chamber 42 from a peripheral portion of the combustion chamber 42. An ignition plug 49 is attached to the lower wall of the cylinder head 41 between the port 44 and the exhaust port 45, and an electrode 49 a at the tip of the ignition plug 49 faces the combustion chamber 42 from near the center of the combustion chamber 42. .
[0007]
Further, in such an engine, in order to create a stratified mixture, which will be described in detail later, one side (for example, one side of the crown surface of the piston 40) is formed in the combustion chamber 42 in order to promote the generation of a reverse tumble vortex of the intake air from the intake port 44. A concave portion 40a having a downwardly convex curved surface is formed in the (intake side) portion, and a raised portion 40b gently rising from the concave portion 40a and approaching the lower surface of the cylinder head 41 at the top dead center of the piston 40. Is formed.
[0008]
On the other hand, the intake pipe 44A and the exhaust pipe 45A are communicated via an EGR pipe 51 provided with an EGR control valve 50, and the exhaust gas is recirculated from the EGR control valve 50 and the EGR pipe 51 to the intake system. This constitutes an EGR device.
[0009]
[Problems to be solved by the invention]
In the direct injection type spark ignition internal combustion engine equipped with such a conventional EGR device, the fuel injected from the fuel injection valve 48 is ignited in order to create a stratified mixture state for enabling lean combustion. The configuration is such that a gas flow to be transported near the electrode 49a of the plug 49 is generated, and the intake port 44 is set upright.
[0010]
That is, in order to make the intake air flowing into the combustion chamber 22 into a so-called reverse tumble vortex in which the swirling direction is the order of the intake valve 46 → the piston 40 → the exhaust valve 47, the direction in which the intake port 44 communicates with the combustion chamber 42. From above the cylinder head 41.
For this reason, compared with a general layout in which the communication direction of the intake port with respect to the combustion chamber is from the side of the cylinder head, there is a problem that the overall height of the engine is increased, and the vehicle mountability of the engine is deteriorated. In addition, there is a problem that the productivity is deteriorated because a large change is required for a general conventional engine.
[0011]
Further, in the conventional engine, the intake pipe 44A and the exhaust pipe 45A are arranged close to each other so that the intake pipe 44A and the exhaust pipe 45A communicate with each other through the short EGR pipe 51. As a result, the intake pipe 44A is heated by this heat, which causes a rise in the temperature of the intake air flow, which lowers the charging efficiency of the engine, and raises the problem that it is not possible to increase the output of the engine.
[0012]
Accordingly, the present invention has been made in view of the conventional problems as described above, and in a direct injection type spark ignition internal combustion engine equipped with an exhaust gas recirculation device, by devising the structure of the exhaust gas recirculation device, etc. It is an object of the present invention to solve the problems that have conventionally occurred while achieving both the reduction in fuel consumption and the reduction in nitrogen oxides (NOx).
[0013]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 is
In a direct injection type spark ignition internal combustion engine, a fuel injection valve directly injects fuel into a combustion chamber formed between a piston crown surface, a cylinder bore inner peripheral surface, and a cylinder head lower surface, and performs spark ignition by a spark plug. ,
A exhaust gas recirculation device for recirculating the exhaust to the intake system, to an intake port and an exhaust port an exhaust valve and an intake valve provided for each cylinder are respectively disposed through communication at its upper position, the upper An exhaust gas recirculation device that includes an exhaust gas recirculation passage disposed in a convex curved shape , and an exhaust gas recirculation control valve interposed in the exhaust gas recirculation passage;
A throttle valve interposed in the intake passage upstream of the intake port;
A fresh air introduction passage communicating with the exhaust gas recirculation passage downstream of the exhaust gas recirculation control valve;
A fresh air control valve interposed in the fresh air introduction passage;
A control unit for controlling the throttle valve, the exhaust gas recirculation control valve, and the fresh air control valve, respectively;
While comprising
The intake port communicates with the combustion chamber from the side of the cylinder head while forming an upwardly convex curved shape ,
When the engine is fully opened, the control unit controls the opening degree of the throttle valve in accordance with the operating state of the engine, closes the exhaust gas recirculation control valve and the fresh air control valve, and burns fresh air only through the intake passage. In the engine partial load operation, the throttle valve is closed, and at least one of the exhaust gas recirculation control valve and the fresh air control valve is opened to introduce the exhaust gas into the combustion chamber. A configuration in which at least fresh air out of the exhaust gas recirculation gas from the passage and the fresh air from the fresh air introduction passage is introduced into the combustion chamber through only the exhaust gas recirculation passage and the intake port to form a reverse tumble vortex in the combustion chamber. And
[0014]
The invention according to claim 2 is
A recess is formed on the intake side of the piston crown surface at a position where the tip injection hole of the fuel injection valve and the tip electrode of the ignition plug face each other.
The invention according to claim 3 is:
The fuel injection valve is disposed on the combustion chamber wall such that its tip injection hole is exposed to the combustion chamber at a position between the intake valve and the exhaust valve and at a position near the intake valve.
The spark plug is disposed on the combustion chamber wall such that the tip electrode is exposed to the combustion chamber at a position between the intake valve and the exhaust valve and near the exhaust valve.
[0015]
The invention according to claim 4 is
The fresh air introduction passage extends parallel to the cylinder row direction of the engine at an upper position near the inlet end of the exhaust gas recirculation passage, and has one end open to the atmosphere and the other end closed. A pipe, and a plurality of fresh air introduction branch pipes branched from the fresh air introduction pipe,
Each fresh air introduction branch pipe is communicated with an upper wall of each exhaust gas recirculation passage near the exhaust gas recirculation control valve,
Each fresh air introduction branch pipe was configured to have the fresh air control valve interposed therebetween.
[0016]
The invention according to claim 5 is
A single exhaust gas recirculation pipe is formed by merging and integrating the base ends of two exhaust gas recirculation passages provided for each cylinder,
The fresh air introduction branch pipe communicates with the junction of the single exhaust gas recirculation pipe,
An exhaust gas recirculation control valve is interposed at the junction of the exhaust gas recirculation pipe,
The fresh air introduction branch pipe was provided with a fresh air control valve interposed.
[0017]
The invention according to claim 6 is
The control unit is configured to perform a control to open the exhaust gas recirculation control valve in the exhaust gas recirculation region and close the exhaust gas recirculation control valve outside the exhaust gas recirculation region during the engine partial load operation.
[0018]
To explain the operation of the present invention, when the engine is fully opened, the intake air amount is large and a large amount of fuel is supplied, so that intake air (fresh air) is introduced only from a normal intake system.
That is, when the engine is fully opened, the opening of the throttle valve is controlled in accordance with the engine operating state, while the exhaust gas recirculation control valve in the exhaust gas recirculation passage and the fresh air control valve in the fresh air introduction passage are both closed.
As a result, the introduction of the exhaust gas recirculation gas from the exhaust passage and the fresh air from the fresh air introduction passage into the exhaust gas recirculation passage is interrupted, and fresh air is introduced into the combustion chamber only from a normal intake system via the intake port. .
[0019]
The intake air flow in the combustion chamber becomes a forward tumble swirl, and the forward tumble swirl causes a mixture of fuel and air directly injected from the fuel injection valve into the combustion chamber to swirl in a recess in the piston crown surface, thereby causing a spark plug. Is ignited.
During partial load operation of the engine , exhaust recirculation is performed as necessary to achieve both lean combustion and NOx reduction.
[0020]
That is, in the exhaust gas recirculation region during the partial load operation, the throttle valve is closed, and the exhaust gas recirculation control valve in the exhaust gas recirculation passage and the fresh air control valve in the fresh air introduction passage are both opened.
As a result, the exhaust gas recirculation gas from the exhaust gas recirculation passage and the fresh air from the fresh air introduction passage are introduced into the exhaust gas recirculation passage, and the exhaust gas recirculation gas and fresh air are introduced into the combustion chamber from the intake port.
[0021]
The intake air flow in the combustion chamber becomes a reverse tumble vortex, and the reverse tumble vortex directs a rich vaporized mixture of fuel injected directly into the combustion chamber from the fuel injection valve in the vicinity of the electrode of the ignition plug. Can be realized. Therefore, lean combustion by stratification is performed.
On the other hand, outside the exhaust gas recirculation region during the partial load operation, the throttle valve is closed, the exhaust gas recirculation control valve in the exhaust gas recirculation passage is closed, and the fresh air control valve in the fresh air introduction passage is opened.
[0022]
Thus, fresh air is introduced from the fresh air introduction passage into the exhaust gas recirculation passage, and only fresh air is introduced into the combustion chamber from the intake port.
As in the case of the exhaust gas recirculation region, the intake air flow in the combustion chamber becomes a reverse tumble vortex, and lean combustion by stratification is performed.
The invention according to claim 7 is
In a direct injection type spark ignition internal combustion engine that directly injects fuel into the combustion chamber and performs spark ignition,
An exhaust recirculation passage arranged in an upwardly convex curved shape so as to communicate the intake port and the exhaust port at an upper position thereof ,
A fresh air introduction passage communicating with the exhaust gas recirculation passage;
Is composed of
The intake port is formed in an upwardly convex curved shape,
In a predetermined operation state, the throttle valve disposed on the upstream side of the intake port is closed, and at least fresh air out of the exhaust gas recirculation gas from the exhaust port and fresh air from the fresh air introduction passage is discharged to the exhaust gas recirculation passage and the intake air. The fuel is introduced into the combustion chamber through a port, and the intake air flow in the combustion chamber forms a reverse tumble vortex in which a rich vaporized mixture of fuel directly injected from the fuel injection valve into the combustion chamber is arranged near the ignition plug. Configuration.
[0023]
【The invention's effect】
According to the invention according to claims 1 and 7 ,
With a general layout in which the communication direction of the intake port with respect to the combustion chamber is from the side of the cylinder head, it is possible to achieve both reduction in fuel consumption by lean combustion and reduction in nitrogen oxides (NOx). The problem that the overall height of the engine becomes higher is eliminated, the mountability of the engine on the vehicle is improved, and significant changes are not required for general conventional engines. it can.
[0024]
In addition, it is not necessary to arrange the intake pipe and the exhaust pipe close to each other in order to connect the intake pipe and the exhaust pipe with a short exhaust gas recirculation pipe as in the conventional case, thereby preventing the intake pipe from being heated by the heat of the exhaust. Therefore, the occurrence of a rise in the temperature of the intake air flow can be suppressed, the charging efficiency of the engine can be improved, and a higher output of the engine can be desired.
Furthermore, since the exhaust gas recirculation passage connects the exhaust port and the intake port of each cylinder to supply the exhaust gas recirculated gas to each cylinder, the distribution of the exhaust gas recirculated gas to each cylinder can be improved. .
[0025]
According to the invention according to claim 2,
The recess in the piston crown suppresses the diffusion of exhaust gas recirculated gas sucked into the combustion chamber and the mixture vaporized in the combustion chamber, and the recess allows a rich mixture gas to be emitted near the spark plug electrode before ignition. It is also effective for stratification distributed in.
According to the invention according to claim 3,
The arrangement of the fuel injector and the spark plug is more advantageous for stratification to achieve lean combustion.
[0026]
According to the invention of claim 4,
The fresh air introduction passage can be effectively formed, and the layout is excellent.
According to the invention according to claim 5,
The configuration can be simplified such that the number of the exhaust gas recirculation passage , the fresh air control valve, and the exhaust gas recirculation control valve can be reduced by half, and the manufacturing cost can be reduced.
[0027]
According to the invention according to claim 6 ,
When the engine is fully opened, the same operation performance as usual can be maintained, and when the engine is under partial load operation, lean combustion due to stratification can be achieved.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a plan view showing an entire four-cycle internal combustion engine which is an embodiment of a direct injection type spark ignition internal combustion engine of the present invention, and FIGS. 2 and 3 are an enlarged plan view and a longitudinal section of a cylinder portion of the engine. FIG.
[0029]
In these figures, a combustion chamber 7 is formed between the crown surface 2A of the piston 2 reciprocated in the cylinder bore 3A of the cylinder block 3, the inner peripheral surface of the cylinder bore 3A and the lower surface of the cylinder head 1. At the upper part of the cylinder head 1 , that is, at the position facing the wall surface of the cylinder head combustion chamber 7 </ b> A formed at the lower part of the cylinder head 1 , two intake ports 4 arranged in parallel and two exhaust ports 5 arranged in parallel are provided. Each intake port 4 is provided with an intake valve 13, and each exhaust port 5 is provided with an exhaust valve 14. Each intake port 4 and each exhaust port 5 are provided with an intake manifold 8 branched from a surge tank 21. The exhaust manifold 9 is connected. An intake pipe 21A is connected to an inlet of the surge tank 21, and a throttle valve 22 for controlling an intake air amount is interposed in the intake pipe 21A.
[0030]
The intake port 4, the intake manifold 8, the surge tank 21, and the intake pipe 21A constitute an intake passage, and the exhaust port 5 and the exhaust manifold 9 constitute an exhaust passage.
The direction in which the intake port 4 forming part of the intake passage and the exhaust port 5 forming part of the exhaust passage communicate with the combustion chamber 7 is set from the side of the cylinder head 1. 5 are arranged so as to extend in directions opposite to each other.
[0031]
Here, the fuel injection valve 18 is for directly injecting fuel supplied from a fuel gallery (not shown) into the combustion chamber 7, and its tip injection hole 18 a is located between the intake valve 13 and the exhaust valve 14. At a position near the valve 13, a wall of the cylinder head 1 facing the crown surface 2 </ b> A of the piston 2 of the combustion chamber 7, so as to be exposed in the combustion chamber 7, and that the center line of the fuel spray forms a predetermined angle with the cylinder center axis. That is, it is disposed on the wall of the cylinder head combustion chamber 7A.
[0032]
The spark plug 20 has the electrode 20a at its tip exposed in the combustion chamber 7 at a position between the intake valve 13 and the exhaust valve 14 and at a position near the exhaust valve 14, and the center line of the electrode 20a is aligned with the cylinder center axis. It is arranged on the wall of the cylinder head combustion chamber 7A so as to form a predetermined angle.
When the engine is in the compression stroke (near top dead center), the crown surface 2A of the piston 2 receives the fuel spray injected from the fuel injection valve 18 toward the intake side, and converts the fuel spray into the spark plug 20. It is formed in a shape facing the electrode 20a.
[0033]
More specifically, a concave portion 30 whose inner surface is concave is located on the intake side of the crown surface 2A of the piston 2 and at a position where the front end injection hole 18a of the fuel injection valve 18 and the front end electrode 20a of the ignition plug 20 face each other. 4 (A)). It should be noted that the shape of the recess 30 shown is an example, and various other shapes such as the recess 30 shown in FIG.
[0034]
Such an in-cylinder direct injection spark ignition internal combustion engine is provided with an EGR device for recirculating exhaust gas to an intake system.
The EGR device includes an EGR pipe 10 as an EGR passage communicating the intake port 4 and the exhaust port 5, and an EGR control valve 11 interposed in the EGR pipe 10.
[0035]
In this case, each of the EGR pipes 10 is disposed above the intake port 4 and the exhaust port 5 in a curved shape that is upwardly convex, and one end of the EGR pipe 10 is connected to each exhaust port 5 and the other end is connected to each intake port. 4 is communicated.
A fresh air introduction passage is connected to the downstream side of each EGR control valve 11 of each EGR pipe 10, and the fresh air control valve 16 is interposed in the fresh air introduction passage 29.
[0036]
The fresh air introduction passage 29 has a plurality of fresh air introduction pipes 29A extending parallel to the cylinder row direction of the engine at an upper position near the inlet end of the EGR pipe 10, and a plurality of branches branched from the fresh air introduction pipe 29A. And a fresh air introduction branch pipe 29B.
One end of the fresh air introduction pipe 29A is opened to the atmosphere via an air filter (not shown), and the other end is closed.
[0037]
Also, each fresh air introduction branch pipe 29B branched from the fresh air introduction pipe 29A is communicated with an upper wall of each EGR pipe 10 near the EGR control valve 11, and the fresh air introduction branch pipe 29B is connected to the fresh air control. Valves 16 are provided respectively.
With this configuration, the exhaust gas recirculation gas from the exhaust port 5 and the fresh air from the fresh air introduction pipe 29A can be introduced from the EGR pipe 10 into the combustion chamber 7 via the intake port 4. The communication port 4 </ b> A to the port 4 is provided with an exhaust valve 13, a piston 2, an exhaust valve, and an exhaust recirculation gas and fresh air flowing from the EGR pipe 10 into the combustion chamber 7 via the intake port 4. The position is set to be a reverse tumble vortex having a turning direction in the order of 14.
[0038]
Specifically, a communication port 4 </ b> A of the EGR pipe 10 to the intake port 4 is set on an upper wall of the intake port 4. Further, a communication port 5 </ b> A of the EGR pipe 10 to the exhaust port 5 is set on an upper wall of the exhaust port 5.
The opening and closing of the EGR control valve 11 and the fresh air control valve 16 at the time of opening / closing and opening are both controlled by a control signal from the control unit 15 based on the engine operating state.
[0039]
This control will be described later in the description of the operation.
Next, the operation of this embodiment will be described separately for each operating state of the engine.
When the engine is fully open (WOT)
When the engine is fully opened and the throttle valve 22 is fully opened, a large amount of intake air and a large amount of fuel are supplied, so intake air (fresh air) is introduced only from the intake manifold 8.
[0040]
That is, in FIG. 5, when the engine is fully opened, the EGR control valve 11 of the EGR pipe 10 and the fresh air control valve 16 of the fresh air introduction passage 29 are both closed by a command from the control unit 15.
As a result, the introduction of the EGR gas from the exhaust passage and the fresh air from the fresh air introduction passage 29 into the EGR pipe 10 is cut off, and fresh air 24 is introduced into the combustion chamber 7 only from the intake manifold 8 via the intake port 4. Is done.
[0041]
The supply amount of the intake air flow is controlled by controlling the opening of the throttle valve 22 by a signal from the control unit 15 based on the operating state of the engine.
The intake air flow in the combustion chamber 7 becomes a forward tumble swirl 31 in the direction indicated by the arrow in FIG. 5, and the forward tumble swirl causes the mixing of the fuel 19 and the air directly injected from the fuel injection valve 18 into the combustion chamber 7. The gas 26 turns in the recess 30 of the piston crown 2A as shown by the arrow in the figure, and is ignited by the spark plug 20.
[0042]
At the time of partial load operation of the engine At the time of partial load operation of the engine, EGR is executed in order to achieve both lean combustion and NOx reduction.
Here, in order to achieve lean combustion and NOx reduction, it is necessary to appropriately set the EGR amount.
[0043]
FIG. 8 is a graph showing the EGR supply amount at which the lean combustion and the NOx reduction are established, and shows that the deposition efficiency ηv when the engine speed is constant and the air-fuel ratio (A / F) = λ is 45%, respectively. (A)), 35% ((b) in the same figure), and 25% ((c) in the same figure) are constant, and the results of operating the engine with the fuel supply at this time fixed are shown.
The horizontal axis of each graph is the A / F, and the vertical axis is the mixture ratio (EGR rate) of the EGR gas to the intake fresh air. In each graph, line a is an EGR gas introduction limit line, line b is an amount of EGR gas required to reduce NOx by 90% or more, and line c is a line required to keep the combustion fluctuation rate within 10%. Of the EGR gas amount.
[0044]
Therefore, by performing the EGR in the region surrounded by the lines a to c of each graph, the operation state is established in which the lean combustion and the NOx reduction are established. Outside the region surrounded by the lines a to c is a region where EGR is not performed.
On the other hand, at the time of lean combustion, it is effective to form a rich mixture in the vicinity of the electrode 20a of the ignition plug 20 at the time of ignition, and to stratify the inside of the combustion chamber 7, and thereby increase the ignition stability. , The lean limit point becomes higher.
[0045]
In order to achieve stratification, it is necessary to have an intake air flow that allows an air-fuel mixture of the injected fuel to exist near the electrode 20a of the ignition plug 20 at the time of ignition. Directly hits the injected fuel, so that the injected fuel is entrapped and lean mixed, and stratification cannot be achieved.
Accordingly, in the EGR range during the partial load operation (see FIG. 8), the command from the control unit 15 causes the EGR control valve 11 of the EGR pipe 10 and the fresh air control of the fresh air introduction passage 29 as shown in FIG. Valves 16 are both opened.
[0046]
Thus, the EGR gas from the exhaust passage and the fresh air from the fresh air introduction passage 29 are introduced into the EGR pipe 10, and the EGR gas and the fresh air are introduced into the combustion chamber 7 from the intake port 4.
The supply amounts of the EGR gas and fresh air are controlled by controlling the opening of the EGR control valve 11 and the opening of the fresh air control valve 16 by a signal from the control unit 15 based on the operating state of the engine. You.
[0047]
The intake air flow in the combustion chamber 7 becomes a reverse tumble swirl 32 indicated by an arrow in the figure, and the reverse tumble swirl 32 removes the rich vaporized mixture 26 by the fuel 19 directly injected from the fuel injection valve 18 into the combustion chamber 7. Since the orientation is such that the ignition plug 20 is arranged near the electrode 20a, stratification can be realized. Therefore, lean combustion by stratification is performed.
[0048]
In FIG. 6, 25 indicates fresh air, and 27 indicates EGR gas.
On the other hand, outside the EGR range during the partial load operation (see FIG. 8), the throttle valve 22 is closed and the EGR control valve 11 of the EGR pipe 10 is closed by the command from the control unit 15, as shown in FIG. It is closed, and the fresh air control valve 16 of the fresh air introduction passage 29 is opened.
[0049]
As a result, fresh air is introduced from the fresh air introduction passage 29 into the EGR pipe 10, and only fresh air is introduced into the combustion chamber 7 from the intake port 4.
Also in this case, the supply amount of fresh air is controlled by controlling the opening degree of the fresh air control valve 16 by a signal from the control unit 15 based on the operating state of the engine.
[0050]
The intake air flow in the combustion chamber 7 becomes a reverse tumble vortex as in the case of the EGR region in FIG. 6, and lean combustion by stratification is performed.
When the engine is running at a low speed When the engine is running at a low speed, the EGR control valve 11 of the EGR pipe 10 is closed and the fresh air control valve 16 of the fresh air introduction passage 29 is opened by a command from the control unit 15.
[0051]
As a result, fresh air is introduced from the fresh air introduction passage 29 into the EGR pipe 10, and only fresh air is introduced into the combustion chamber 7 from the intake port 4.
Accordingly, stratification is similarly achieved, ignition stability is improved, and fuel efficiency is improved.
According to the embodiment described above, nitrogen oxides (NOx) can be reduced while realizing fuel consumption reduction by lean combustion, and the conventional problems can be solved as follows.
[0052]
That is, a general layout in which the communication direction of the intake port 4 with respect to the combustion chamber 7 is from the side of the cylinder head 1 can be achieved, and the problem of an increase in the overall height of the engine can be eliminated. Is improved, and significant changes are not required for general conventional engines, so that productivity can be improved.
Further, unlike the related art, in order to connect the intake pipe and the exhaust pipe with the short EGR pipe, it is not necessary to make the intake pipe and the exhaust pipe close to each other, and it is possible to prevent the intake pipe from being heated by the heat of the exhaust gas. Therefore, the occurrence of a rise in the temperature of the intake air flow can be suppressed, the charging efficiency of the engine can be improved, and a higher output of the engine can be expected.
[0053]
Furthermore, according to the above configuration, the EGR pipe 10 is used to connect the exhaust port 5 and the intake port 4 of each cylinder so that EGR gas is supplied to each cylinder. Gas distribution can be improved.
Further, since the recess 30 is provided in the piston crown surface 2A, the diffusion of the EGR gas sucked into the combustion chamber 7 and the gas mixture vaporized in the combustion chamber 7 can be suppressed. This is also effective for stratification in which a rich gas mixture is distributed in the vicinity of the electrode 20a of the ignition plug 20 before.
[0054]
In the above-described embodiment, two new air introduction branch pipes 29B branched from the new air introduction pipe 29A are provided for each cylinder, and these are connected to the two EGR pipes 10 provided for each cylinder. As shown in FIG. 9, a single EGR pipe 10A is formed by merging and integrating the base ends of two EGR pipes 10 provided for each cylinder, and a fresh air introduction pipe is provided for each cylinder. One new air introduction branch pipe 29C branching from 10 is provided, and this is connected to the junction of the single EGR pipe 10A, and the new air control valve 16 is interposed in each one new air introduction branch pipe 29C. Alternatively, the EGR control valve 11 may be interposed at the junction of the single EGR pipe 10A.
[0055]
According to such a configuration, the number of EGR pipes, fresh air control valves, and EGR control valves can be reduced by half, so that the configuration can be simplified, and the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing one embodiment of a direct injection type spark ignition internal combustion engine of the present invention. FIG. 2 is a plan view of the same embodiment. FIG. 3 is a plan view of the entire engine of the same embodiment. FIG. 4 is a plan view showing the shape of a piston crown surface. FIG. 5 is a longitudinal sectional view for explaining the operation of the embodiment. FIG. 6 is a longitudinal sectional view for explaining the operation of the embodiment. FIG. 8 is a graph showing an EGR supply amount at which lean combustion and NOx reduction are realized. FIG. 9 is a plan view of the entire engine showing another embodiment. FIG. FIG. 11 is a longitudinal sectional view showing an injection type spark ignition internal combustion engine. FIG. 11 is a plan view of the same.
Reference Signs List 1 cylinder head 2 piston 2A piston crown 3A cylinder bore 4 intake port 4A communication port 5 exhaust port 7 combustion chamber 10 EGR pipe 11 EGR control valve 13 intake valve 14 exhaust valve 15 control unit 16 fresh air control valve 18 fuel injection valve 18a injection Hole 20 Spark plug 20a Electrode 29 Fresh air inlet passage 29A Fresh air inlet tube 29B Fresh air inlet branch tube 29C Fresh air inlet branch tube 30 recess

Claims (7)

In a direct injection type spark ignition internal combustion engine, a fuel injection valve directly injects fuel into a combustion chamber formed between a piston crown surface, a cylinder bore inner peripheral surface, and a cylinder head lower surface, and performs spark ignition by a spark plug. ,
A exhaust gas recirculation device for recirculating the exhaust to the intake system, to an intake port and an exhaust port an exhaust valve and an intake valve provided for each cylinder are respectively disposed through communication at its upper position, the upper An exhaust gas recirculation device that includes an exhaust gas recirculation passage disposed in a convex curved shape , and an exhaust gas recirculation control valve interposed in the exhaust gas recirculation passage;
A throttle valve interposed in the intake passage upstream of the intake port;
A fresh air introduction passage communicating with the exhaust gas recirculation passage downstream of the exhaust gas recirculation control valve;
A fresh air control valve interposed in the fresh air introduction passage;
A control unit for controlling the throttle valve, the exhaust gas recirculation control valve, and the fresh air control valve, respectively;
While comprising
The intake port communicates with the combustion chamber from the side of the cylinder head while forming an upwardly convex curved shape ,
When the engine is fully opened, the control unit controls the opening degree of the throttle valve in accordance with the operating state of the engine, closes the exhaust gas recirculation control valve and the fresh air control valve, and burns fresh air only through the intake passage. In the engine partial load operation, the throttle valve is closed, and at least one of the exhaust gas recirculation control valve and the fresh air control valve is opened to introduce the exhaust gas into the combustion chamber. At least fresh air out of the exhaust gas recirculation gas from the passage and the fresh air from the fresh air introduction passage is introduced into the combustion chamber only through the exhaust gas recirculation passage and the intake port to control the formation of a reverse tumble vortex in the combustion chamber. An in-cylinder direct injection spark ignition internal combustion engine. The in-cylinder direct injection spark according to claim 1, wherein a recess is formed on the intake side of the piston crown surface at a position where a tip injection hole of a fuel injection valve and a tip electrode of a spark plug face each other. Ignition internal combustion engine. The fuel injection valve is disposed on the combustion chamber wall such that its tip injection hole is exposed to the combustion chamber at a position between the intake valve and the exhaust valve and at a position near the intake valve.
3. The ignition plug according to claim 1, wherein the spark plug is disposed on a wall of the combustion chamber such that a tip electrode thereof is exposed to the combustion chamber at a position between the intake valve and the exhaust valve and at a position near the exhaust valve. An in-cylinder direct injection spark ignition internal combustion engine according to claim 1. The fresh air introduction passage extends parallel to the cylinder row direction of the engine at an upper position near the inlet end of the exhaust gas recirculation passage, and has one end open to the atmosphere and the other end closed. A pipe, and a plurality of fresh air introduction branch pipes branched from the fresh air introduction pipe,
Each fresh air introduction branch pipe is communicated with an upper wall of each exhaust gas recirculation passage near the exhaust gas recirculation control valve,
The direct injection type spark ignition internal combustion engine according to any one of claims 1 to 3, wherein the fresh air control valve is interposed in each fresh air introduction branch pipe. A single exhaust gas recirculation pipe is formed by merging and integrating the base ends of two exhaust gas recirculation passages provided for each cylinder,
The fresh air introduction branch pipe communicates with the junction of the single exhaust gas recirculation pipe,
An exhaust gas recirculation control valve is interposed at the junction of the exhaust gas recirculation pipe,
5. The direct injection type spark ignition internal combustion engine according to claim 4, wherein a fresh air control valve is interposed in the fresh air introduction branch pipe . The control unit performs control of opening the exhaust gas recirculation control valve in an exhaust gas recirculation region and closing the exhaust gas recirculation control valve outside the exhaust gas recirculation region during engine partial load operation. Item 6. An in-cylinder direct injection spark ignition internal combustion engine according to any one of Items 1 to 5. In a direct injection type spark ignition internal combustion engine that directly injects fuel into the combustion chamber and performs spark ignition,
An exhaust recirculation passage arranged in an upwardly convex curved shape so as to communicate the intake port and the exhaust port at an upper position thereof,
A fresh air introduction passage communicating with the exhaust gas recirculation passage;
Is composed of
The intake port is formed in an upwardly convex curved shape,
In a predetermined operation state, the throttle valve disposed on the upstream side of the intake port is closed, and at least fresh air out of the exhaust gas recirculation gas from the exhaust port and fresh air from the fresh air introduction passage is discharged to the exhaust gas recirculation passage and the intake air. The fuel is introduced into the combustion chamber through a port, and the intake air flow in the combustion chamber forms a reverse tumble vortex in which a rich vaporized mixture of fuel directly injected from the fuel injection valve into the combustion chamber is arranged near the ignition plug.
An in- cylinder direct injection spark ignition internal combustion engine characterized by the above-mentioned.

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