JP2003193841A - Engine for stratified combustion at stoichiometric air-fuel ratio and stratified combustion method for the engine - Google Patents

Abstract

(57) [Problem] To achieve stratified combustion near the stoichiometric air-fuel ratio with EGR gas to reduce pumping loss and improve fuel efficiency, to prevent deterioration of fuel efficiency due to rich spikes, and to achieve high exhaust gas. An in-cylinder injection engine capable of obtaining a purification effect and a stratified combustion method for the engine are provided. The engine includes a fuel injection valve for directly injecting fuel in a cylinder, and a spark plug for igniting a mixture of the fuel and intake air in the cylinder. Air-fuel mixture stratification means for stratifying the air-fuel mixture during the stratified charge combustion operation, wherein the air-fuel mixture stratification means forms the air-fuel mixture layer near the ignition plug to perform stratified combustion at a stoichiometric air-fuel ratio. At the same time, an EGR gas layer is formed around the air-fuel mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder injection type engine and a combustion method for the engine, and more particularly to a cylinder injection type engine and a stratification combustion method for the engine, which realize a stratified combustion operation at a stoichiometric air-fuel ratio. Regarding

[0002]

2. Description of the Related Art Today's automobiles include carbon monoxide CO and hydrocarbons H contained in the exhaust gas of automobiles from the viewpoint of environmental protection.
Further reduction of exhaust substances such as C and nitrogen oxide NOx is required. As an example aimed at reducing these,
Examples include lean stratified combustion engines. This is to stratify and burn a mixture of fuel and intake air by using in-cylinder air activity by a tumble flow.
We are working to reduce fuel consumption and CO emissions.

As an example of these systems, for example, the technique disclosed in Japanese Patent Laid-Open No. 6-159079 has been proposed. According to the proposed technique, a partition is provided in the intake port, the partition divides the intake port into four sections of a center, a left, a right, and a bypass port, and a tumble control valve is provided at an inlet of the bypass port. That is, when the engine is running at low speed and low load, the tumble control valve is closed and fuel is injected into the central port. As a result, a tumble flow is generated in the combustion chamber, stratification of the air-fuel mixture is performed, stable combustion can be performed even in a lean air-fuel mixture, and combustion can be promoted to improve fuel efficiency. It is a technology that can be done.

As another example of stratification of the air-fuel mixture, various engine technologies using EGR gas have been proposed (for example, JP-A-8-82233 and JP-A-9-42070). Japanese Patent Laid-Open No. 11-21
58, etc.). Further, from the viewpoint of the current state of global warming and resource conservation in recent years, a technique of a cylinder injection engine is known in order to reduce fuel consumption and CO2.

[0005]

By the way, the above-mentioned conventional technique, in particular, the technique disclosed in Japanese Unexamined Patent Publication No. 6-159079 discloses an emission because a stratified combustion is performed using a lean mixture gas. A three-way catalyst conventionally used for purification of (exhaust gas) has a disadvantage that it has no effect on purification.

Therefore, in order to solve this, especially NOx
A lean NOx catalyst is generally used for the purification of NOx. The lean NOx catalyst is
Ox is adsorbed, and then rich spike is performed, that is, the air-fuel ratio of the exhaust gas is made rich (enriched) to about 13 at regular intervals, and the N adsorbed during the lean operation is adsorbed.
It is a catalyst that needs to reduce Ox.

That is, during the rich spike period, the stratified charge combustion using the lean air-fuel mixture cannot be performed, and the energy for reducing the NOx, in other words, wasted fuel is consumed. . As described above, if the fuel is consumed excessively, even if the fuel consumption is reduced by the lean air-fuel mixture so far, it is offset by the fuel supply by the rich spike, and the actual fuel consumption reduction rate is There was a problem that it decreased.

In the current technology, the lean NOx is used.
The purification rate of NOx by the catalyst is about 90% at the maximum, which is lower than the purification rate of 99% in the case of the three-way catalyst, which causes deterioration of the emission from the final tail pipe, that is, the exhaust pipe. The problem still remains.

Further, in stratification with a lean mixture,
Since the amount of air is limited by the intake negative pressure of the engine, the intake air cannot be supplied any more even when the load of the engine is required to be high, and the lean air-fuel mixture does not meet the required operation. However, there is also a problem that the torque that can be stratified is limited to a low level because it cannot be performed.

That is, in order to further increase the added value of the in-cylinder injection engine, the inventor of the present invention does not perform rich spikes during stratified charge combustion operation, or reduces the number of rich spikes as much as possible to prevent deterioration of fuel consumption. The present inventors have obtained a new finding that a stratified combustion system capable of achieving the above can be obtained, and have derived a configuration in which EGR gas, which is exhaust gas recirculation, is used to wrap an air-fuel mixture to perform stratified combustion near the stoichiometric air-fuel ratio. However, in the conventional technique, the passage outlet of the EGR gas exists near the collector of the intake pipe, the EGR gas is premixed with intake air and supplied into the cylinder, and the EGR gas Even if the passage outlet is located near the cylinder, no special consideration is given to the positional relationship between the air-fuel mixture and the EGR gas for stratified combustion near the stoichiometric air-fuel ratio.

The present invention has been made in view of the above problems, and an object thereof is to perform stratified combustion near the stoichiometric air-fuel ratio with EGR gas to reduce pumping loss and improve fuel efficiency. It is an object of the present invention to provide a cylinder injection type engine that can prevent deterioration of fuel efficiency due to rich spike and can obtain a high exhaust gas purification effect, and a method for stratified combustion of the engine.

[0012]

[Means for Solving the Problems] To achieve the above object,
An engine that performs stratified combustion at a stoichiometric air-fuel ratio according to the present invention includes a fuel injection valve that directly injects fuel in a cylinder, and an ignition plug that ignites a mixture of the fuel and intake air in the cylinder. The engine includes a mixture stratification means for stratifying the air-fuel mixture during stratified charge combustion operation, the stratification means for stratifying the air-fuel mixture comprises the spark plug for stratified combustion at a stoichiometric air-fuel ratio. A layer of the air-fuel mixture is formed in the vicinity, and EG is formed around the air-fuel mixture.
It is characterized in that a layer of R gas is formed.

In the engine having the stoichiometric air-fuel ratio of the present invention configured as described above, the mixture stratification means forms a layer of the mixture near the ignition plug during stratified combustion operation, and the mixture is formed. Since it functions so as to be surrounded by a layer of EGR gas, stratified combustion near the stoichiometric air-fuel ratio is possible in the cylinder, which improves fuel efficiency by reducing engine pumping loss and eliminates the need for rich spikes. As a result, the fuel consumption can be further improved, and the value of the direct injection engine can be further enhanced.

Further, in a specific mode of the engine for performing stratified combustion at a stoichiometric air-fuel ratio according to the present invention, the mixture stratification means is at least one of a plurality of intake passages formed by partitioning an intake pipe. An intake control valve for opening and closing one intake passage is provided, and a passage outlet for the EGR gas is provided between the intake control valve and the cylinder of the opened and closed intake passage.

Further, in another specific embodiment of the engine for performing stratified combustion at the stoichiometric air-fuel ratio according to the present invention, the mixture stratification means produces two tumble flows in the cylinder, One of the tumble flows is the flow of the intake air from the intake valve toward the piston along the exhaust valve, and the other of the tumble flows is the flow of the EGR gas toward the exhaust valve along the upper surface of the piston. Or the spray of the fuel injection valve is a deflected spray to the spark plug side and has a penetrating force for passing through the other tumble flow and mixing with the one tumble flow. There is.

Still another specific embodiment of the engine that performs stratified combustion at a stoichiometric air-fuel ratio according to the present invention is that the mixture stratification means produces two swirl flows in the cylinder. , One of the swirl flows is a flow of the EGR gas along the side wall surface of the cylinder,
The other of the swirl flows is a flow in a direction opposite to that of the one swirl flow, and is a flow for arranging the intake air inside the EGR gas.

The air-fuel mixture stratification means forms a layer of the air-fuel mixture in the vicinity of the spark plug, forms a layer of the EGR gas around the air-fuel mixture, and further forms the layer of EGR gas.
Forming a layer of the intake air around the GR gas, or forming the layer of the air-fuel mixture in the vicinity of the spark plug and forming a layer of the air-intake around the air-fuel mixture And further forming a layer of the EGR gas around the intake air, or the fuel injection valve injects fuel in the latter half of the compression stroke during the stratified charge combustion operation, and in the intake stroke during the homogeneous combustion operation. It is characterized by injecting fuel.

Further, the engine that performs stratified combustion at a stoichiometric air-fuel ratio according to the present invention is a fuel injection valve that directly injects fuel in a cylinder, and an ignition plug that ignites a mixture of the fuel and air in the cylinder. And an engine including a mixture stratification means for stratifying the mixture so that the air-fuel ratio in the cylinder during stratified charge combustion operation becomes a stoichiometric air-fuel ratio. A three-way catalyst that purifies exhaust gas during the stratified charge combustion operation is provided, and it becomes possible to use a three-way catalyst having a high NOx removal rate of about 99%, which reduces the system cost and The effect of purifying the exhaust gas can be further increased, which also enhances the value of the direct injection engine.

Further, the stratified combustion method by the stoichiometric air-fuel ratio of the engine according to the present invention includes an intake control valve for opening and closing at least one intake passage among a plurality of intake passages formed by partitioning the intake pipe, A mixture mixture stratification means for stratifying a mixture of fuel and intake air at the time of stratified combustion operation, having an EGR gas passage outlet between the cylinder of the intake passage to be opened and closed and the cylinder. A stratified combustion method for an engine, in which the air-fuel mixture is stratified and burned in the cylinder, wherein the intake control valve is closed to fill the intake passage opened and closed with the EGR gas, and then the intake air of the engine is taken. In the stroke, a flow that causes the intake air to flow into the cylinder from an intake passage other than the opened / closed intake passage is generated, and the cylinder is opened from the opened / closed intake passage. A flow for causing the EGR gas to flow in is generated, and the fuel injection valve injects in the compression stroke of the engine to form a layer of the air-fuel mixture in the vicinity of the spark plug and A layer of the EGR gas is formed around the to form a stratified mixture according to the stoichiometric air-fuel ratio in the cylinder.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an engine (theoretical air-fuel ratio stratified combustion engine) that performs stratified combustion at a stoichiometric air-fuel ratio in the first embodiment of the present invention. The engine 50
Consists of multiple cylinders, and each cylinder 123 has an intake pipe 1
01 and the exhaust pipe 110 include an intake valve 111 and an exhaust valve 112.
Cylinder 1
23, a fuel injection valve 122 for directly injecting fuel,
A spark plug 113 for igniting a mixture of fuel and intake air in the cylinder 123 is provided. The fuel injection valve 122 is provided on the intake pipe 101 side of the cylinder 123, and the spark plug 113 is provided above the cylinder 123.

The intake pipe 101 includes an upper intake passage 101.
A and a lower intake passage 101b are divided into upper and lower partitions 114, and an upstream end of the partition 114 has an intake control valve (tumble control valve) for opening and closing the lower intake passage 101b. 102 is provided. Further, in the lower intake passage 101b, the tumble control valve 102
A passage outlet 109e for EGR gas, which is exhaust gas recirculation described later, is provided between the cylinder 123 and the cylinder 123.
The EGR gas is introduced into the cylinder 123 along the curved upper surface of the piston 107 as described later.

The air sucked from the right side of FIG. 1 passes through the air cleaner 106, the flow rate of the air is measured by the air flow meter 105, and the flow rate is adjusted by the electronically controlled throttle chamber 104, and then the collector 103 of each cylinder 123. Will be distributed to. Then, the intake pipe 101 described above
And is introduced into the cylinder 123 when the intake valve 111 is opened.

The fuel injection valve 122 injects fuel in the latter half of the compression stroke during the stratified charge combustion operation, and injects the fuel during the intake stroke during the homogeneous combustion operation, and forms an air-fuel mixture with the intake air. The air is burned in the cylinder 123 by the ignition of the spark plug 113. In addition, the spray of the fuel injection valve 122 is, as shown in the figure, the spark plug 11
The so-called deflected spray 125 is used in which the amount toward the 3 side is large and the speed is high.

The gas burned in the cylinder 123 passes through the exhaust valve 112 and the exhaust pipe 110, and then the three-way catalyst 115.
And is released into the atmosphere through a muffler (not shown).
While the flow rate is adjusted by the control valve 108, the EGR passage 1
The EGR gas is recirculated from the EGR gas passage outlet 109e to the lower intake passage 101b through the passage 09.

The fuel injection timing of the fuel injection valve 122, the ignition timing of the spark plug 113, the opening of each of the tumble control valve 102, the electronically controlled throttle chamber 104, and the EGR control valve 108 are the intake air measured by the air flow meter 105. The computer 201 sets and controls the optimum value and timing based on information such as the amount, the accelerator opening, the engine water temperature, the engine speed, and the vehicle speed (none of which is a sensor for inputting the input).

In the engine 50 of this embodiment, the gas mixture stratification means 10 for stratifying the gas mixture so that the entire gas in the cylinder 123 is stratified and burned at the stoichiometric air-fuel ratio.
0, and the gas mixture stratification means 100 of the present embodiment.
Has a partition 114, a tumble control valve 102, and an EGR gas passage outlet 109e.

That is, the gas mixture stratification means 1 of this embodiment.
00 functions as a tumble generation mechanism that generates a tumble flow in the cylinder 123, and the tumble flow 120 in the upper intake passage 101a and the lower intake passage 1
Two tumble streams, the tumble stream 121 of 01b, are generated.

As shown in the figure, the tumble flow 120 in the upper intake passage 101a is such that the intake air from the collector 103 flows from the intake valve 111 to the exhaust valve 112 along with the piston 10.
7 (forward tumble), and the tumble flow 121 in the lower intake passage 101b is a flow (reverse tumble) toward the exhaust valve 112 after the EGR gas is directed along the upper surface of the piston 107.

Specifically, in the case of performing stratified charge combustion as in this embodiment, the mixture stratification means 100 first closes the tumble control valve 102 to close the lower intake passage 101b and then EGR. EGR gas is made to flow into and fill the lower intake passage 101b via the passage 109 and the EGR control valve 108.

Next, when the piston 107 descends and the intake valve 111 opens in the intake stroke of the engine 50, the intake air passing through the upper intake passage 101a flows into the cylinder 123 through the upper side of the intake valve 111. Then, the forward tumble 120 is formed. Meanwhile, at the same time, the lower intake passage 101
The EGR gas filled in b flows through the lower side of the intake valve 111 into the cylinder 123, and the reverse tumble 121
To form.

Then, as shown, the inverse tumble 121
Becomes a flow along the piston 107, and the cylinder 123
Stays below. Forward tumble 120 is reverse tumble 1
It is located above 21 and flows in the vicinity of the spark plug 113. Subsequently, in the compression stroke of the engine 50, the intake valve 111 is closed, the piston 107 moves up, and the air in the cylinder 123 is compressed. At this time, the fuel injection valve 122 passes through the reverse tumble 121 and passes through. , The fuel pressure and the like are optimally adjusted so that the injection having the penetration (penetration force) of vaporizing and mixing when reaching the forward tumble 120 is made, and the upward component of the figure is lower than the downward component. This is the deflected spray 125 that also becomes larger, and the efficient mixing of the forward tumble 120 that has come out from the upper side of the intake valve 111 and the fuel is performed.

As described above, the mixture stratification means 100 of the present embodiment generates the two tumble streams 120 and 121, the layer of the mixture is present in the vicinity of the spark plug 113, and the surroundings of the mixture. A layer of the EGR gas is present in the cylinder, and the air-fuel mixture is surrounded by the EGR gas, so that stratified combustion by the stoichiometric air-fuel ratio is enabled in the cylinder 123 instead of the lean air-fuel ratio. There is. And the exhaust gas at the time of this stratified charge combustion operation,
Since it is adjusted to be close to the stoichiometric air-fuel ratio as described above, it oxidizes hydrocarbons HC and carbon monoxide CO, and nitrogen oxides NO
It is purified by the three-way catalyst 115 having a purification function of reducing x.

2 to 4 show an air-fuel mixture and an EG according to the engine load by the air-fuel mixture stratification means 100 of the present embodiment.
This is a description of stratification with R gas. Figure 2
[Fig. 6] is an operation explanatory view in an engine low load region. In the engine low load region, first, the opening of the electronically controlled throttle chamber 104 is set to be small by a signal from the computer 201. On the other hand, the opening degree of the EGR control valve 108 is set large. As a result, in the intake stroke of the engine 50, when the intake valve 111 is opened, the gas sucked into the cylinder 123 is not discharged into the upper intake passage 10.
Intake passage 101b below the intake air passing through 1a
The EGR gas that has passed through becomes larger, that is, the amount of the reverse tumble 121 is larger than that of the forward tumble 120, and the flow becomes stronger.

However, in this case as well, the forward tumble 120 flows near the ignition plug 113, and since it is the deflected spray 125, the fuel injection valve 122.
The fuel from is mixed with the forward tumble 120 while minimizing mixing with the reverse tumble 121,
A stoichiometric air-fuel ratio mixture is formed around 13. The reverse tumble 121 stays below the cylinder 123 and increases the intake gas amount (air + EGR gas) while keeping the air-fuel ratio in the cylinder 123 close to the stoichiometric air-fuel ratio, reducing pumping loss and cooling loss. Can be made.

FIG. 3 is a diagram for explaining the operation in the engine middle load range. In the medium load region of the engine, first, the opening of the electronically controlled throttle chamber 104 is set to be slightly larger than that in the low load region by a signal from the computer 201. On the other hand, the opening degree of the EGR control valve 108 is set to be slightly smaller than that in the low load range. As a result, the engine 50
In the intake stroke of, when the intake valve 111 opens,
As for the gas sucked into the cylinder 123, the intake air that has passed through the upper intake passage 101a is lower in the lower intake passage 10a.
It becomes larger than the EGR gas that has passed through 1b, that is, the amount of the forward tumble 120 is larger than that of the reverse tumble 121, and the flow becomes stronger.

At this time, the EGR gas of the reverse tumble 121 stays in the vicinity of the piston 107, and the spark plug 113
The forward tumble 120 flows in the other part of the cylinder 123 including the vicinity of the forward tumble 120, and the fuel from the fuel injection valve 122 is mixed with the reverse tumble 121 while minimizing the mixing with the forward tumble 120. As a result of mixing, a mixture of stoichiometric air-fuel ratio is formed around the spark plug 113.

Also in this case, the intake gas amount is increased while maintaining the air-fuel ratio in the entire cylinder 123 near the stoichiometric air-fuel ratio, and pumping loss and cooling loss can be reduced. 2 and 3, the ratio of the air-fuel mixture to the EGR gas varies depending on the engine operating state, but the intake air amount is the standard, that is, 100.
When set to%, as will be described later, for example, 0% to 1
It can also be set by changing it to about 50%.

Further, in the medium load condition of the engine 50, the pressure of the EGR gas which has passed through the EGR passage 109 is higher than that of the prior art, which is mainly the case of stratified combustion using air. Therefore, when the EGR control valve 108 is set in the vicinity of full open, it becomes higher than the pressure of the air passing through the intake pipe 101. That is, the inverse tumble 121 is a conventional technique,
Since the maximum flow rate can be increased in the case of the stratified combustion mainly using EGR gas as in the present embodiment, the upper limit of the load capable of the stratified combustion is higher than in the case of the stratified combustion mainly including the air. It is possible to widen the area in which the stratified charge combustion operation is possible.

FIG. 4 is a diagram for explaining the operation in the high engine load region. In the engine high load range, first, the opening of the electronically controlled throttle chamber 104 is set to be larger than that in the medium load range (close to full open) by the signal from the computer 201, and the tumble control valve 102 is opened.
Is set to open. On the other hand, the opening degree of the EGR control valve 108 is set to be smaller than that in the medium load range. As a result, the intake resistance is reduced. Therefore, in the intake stroke of the engine 50, when the intake valve 111 is opened, a large amount of fresh air is introduced into the cylinder 123 from both the upper intake passage 101a and the lower intake passage 101b. To supply.

At this time, in the intake stroke of the engine, the signal from the computer 201 causes a signal injection from the fuel injection valve 122.
Is injecting fuel, the vaporization time and diffusion time of the spray are lengthened to promote mixing with the intake air, and the cylinder 12
The homogeneity within 3 is increased. Then, a large torque is obtained by increasing the fuel injection amount and forming a large amount of air-fuel mixture.

FIG. 5 is an operation flowchart in each engine load region shown in FIGS. 2 to 4. In step 1, the computer 201 reads the engine speed, the accelerator opening, the water temperature, the intake pressure, the exhaust temperature, and the gear position from the respective sensors, and based on these, calculates the target torque in step 2, and then proceeds to step 3. Then, the fuel injection amount is determined and the process proceeds to step 4. In Step 4, the target torque is used to refer to the operating state map of the engine speed and the load, and it is checked whether the region is in the stratified charge combustion operation or the homogeneous combustion operation. Then, in step 5, the ignition timing is determined.

Next, at step 6, it is judged whether or not it is in the stratified charge combustion operation mode. If it is in the stratified charge combustion operation mode, that is, if YES, the routine proceeds to step 7, where the mixture stratification means 100 is The tumble control valve 102 is closed, the fuel injection timing of the fuel injection valve 122 is set to the compression stroke of the engine 50 in step 8, and the process proceeds to step 9.

On the other hand, in step 6, when the stratified charge combustion operation is not performed, that is, in the homogeneous combustion operation mode,
In step 10, the tumble control valve 102 is opened, the fuel injection timing is set in the intake stroke of the engine 50 in step 11, and the process proceeds to step 9. Then, in step 9, the opening degree of the electronically controlled throttle chamber 104 is set to a predetermined amount according to each engine load, and in step 12,
Similarly, the opening degree of the EGR control valve 108 is set to a predetermined amount corresponding to each engine load, and the process proceeds to step 13.

In step 13, the intake valve 111 is opened in the intake stroke of the engine 50, and in step 14, it is judged whether or not it is the stratified charge combustion operation mode. If it is the stratified charge combustion operation mode, that is, YES is determined. At this time, the process proceeds to step 15, and since the tumble control valve 102 is already closed, the mixture stratification means 100 generates the forward tumble 120 by the intake air and the reverse tumble 121 by the EGR, and at step 16, The fuel injection valve 122 directs the forward tumble 120 to inject fuel in the compression stroke,
In step 17, a layer of air-fuel mixture is formed around the spark plug 113, and a layer of EGR gas is formed around the layer to achieve stratification, and the process proceeds to step 18, where the spark plug 11
3 ignites the air-fuel mixture, burns in the vicinity of the stoichiometric air-fuel ratio in the cylinder 123, and ends a series of operations.

On the other hand, if the homogeneous combustion operation mode is selected in step 14, the tumble control valve 102 is already opened in step 19, so that the upper intake passage 10 is opened.
Air flows in from both 1a and the lower intake passage 101b. At this time, a large amount of air is supplied into the cylinder 123 because the passage sectional area of the intake pipe is large and the resistance is small. Then, in step 20, the fuel injection valve 122
However, the fuel injection can be performed during the intake stroke to increase the vaporization time, and in step 21, the homogeneity of the air-fuel mixture in the cylinder 123 is increased. Is ignited and a series of operations is completed. Then, the outputs from these combustions are taken out, and then the combustion gas is discharged to the exhaust passage 110 side in the exhaust stroke of the engine 50, and one cycle is completed. After that, similarly, the operation of the engine 50 that repeats this operation is performed.

FIGS. 6 and 7 are configuration diagrams of an engine that performs stratified combustion at a stoichiometric air-fuel ratio in the second embodiment of the present invention. Here, while the mixture stratification means 100 of the first embodiment forms a tumble flow that swirls in the longitudinal axis direction in the cylinder 123 during intake,
The mixture stratification means 100A of the present embodiment forms a swirl flow swirling in the direction perpendicular to the longitudinal axis. Therefore, the present embodiment is the same as the first embodiment except for this point in the other configuration and the like, and therefore the different points will be mainly described.

That is, first, in the piston 107A used in this embodiment, as shown in FIG. 6, a cavity 301 provided near the center of the piston 107A.
And a concave surface 302 along the outer peripheral direction of the cavity 301 are respectively provided as a passage for a swirl flow 304 in one intake passage 305b and a swirl flow 303 from the other intake passage 305a, as will be described later. .

FIG. 7 is a block diagram of an engine that performs stratified combustion at the stoichiometric air-fuel ratio in this embodiment.
The cylinder 123A of A has an intake pipe 101 and an exhaust pipe 11.
0 are connected via two intake valves 111, 111 and two exhaust valves 112, 112, respectively, and one intake passage 305b and the other intake passage 305a are connected to the intake pipe 101 at the left and right. The one intake passage 305b is provided with an intake control valve 306 for opening and closing the intake passage 305b. Further, in the one intake passage 305b, between the intake control valve 306 and the cylinder 123A, the EGR gas passage outlet 1 is provided.
09e is provided. The other intake pipe 101
The configuration of the exhaust pipe 110, the configuration and control of the fuel injection valve 122, the computer 201, the spark plug 113, and the like are the same as those in the first embodiment, and thus description thereof is omitted.

The engine 50A of the present embodiment is also equipped with a gas mixture stratification means for stratifying the air-fuel mixture so as to stratify the entire gas in the cylinder 123A at the stoichiometric air-fuel ratio. Mixture stratification means 10
OA has an intake control valve 306 and a passage outlet 109e for EGR gas.

That is, the gas mixture stratification means 1 of this embodiment.
00A functions as a swirl generation mechanism that generates a swirl flow in the cylinder 123, and generates two swirl flows, a swirl flow 304 in one intake passage 305b and a swirl flow 303 in the other intake passage 305a. is doing.

As shown in the figure, the swirl flow 304 in one intake passage 305b is a flow around the hour hand that causes the EGR gas to go along the inner wall surface of the cylinder 123, and the swirl flow 303 in the other intake passage 305a is the one described above. Is a flow around the counter hour hand in the opposite direction to the swirl flow 304, and is a flow for arranging the intake air from the collector 103 inside the EGR gas.

Specifically, when performing the stratified charge combustion of the present embodiment, first, the mixture stratification means 100A closes the intake control valve 306 to close one intake passage 305b,
EGR via EGR passage 109 and EGR control valve 108
Gas is made to flow into one of the intake passages 305b to be filled.

Next, in the intake stroke of the engine 50A, the piston 107A descends and the intake valves 111, 111 open,
The intake air that has passed through the other intake passage 305a flows into the cylinder 123A through the upper side of the intake valve 111 on one side, flows along the cavity 301 on the piston 107, and rotates in the counterclockwise direction as shown. A swirl 303 is formed.

On the other hand, at the same time, the EGR gas filled in the intake passage 305b flows along the concave surface 302 on the piston 107 to form a swirl 304 rotating in the hour hand direction as shown in the figure. Then, as shown in the figure, E
The swirl 304 of the GR gas stays inside the cylinder 123 on the side wall surface side facing the one intake passage 305b. The swirl 303 of the intake air is located inside the swirl 304 and has a flow passing near the spark plug 113.

Subsequently, in the compression stroke of the engine 50A, the intake valves 111, 111 are closed and the piston 107A is closed.
Rises and the air in the cylinder 123A is compressed. At this time, in the fuel injection valve 122 arranged below the intake passages 305a and 305b, the fuel spray 125 causes the swirl 3
Optimum adjustment of the fuel pressure and the like is performed so that the injection having the penetration (penetration force) of directing the gas toward the fuel injection port 03 and vaporizing and mixing in the swirl 303 is performed.

As described above, the air-fuel mixture stratifying means 100A of the present embodiment generates the two swirl flows 303 and 304, the air-fuel mixture layer is present in the vicinity of the spark plug 113, and the air-fuel mixture is surrounded by the air-fuel mixture. A layer of the EGR gas is present in the cylinder, and the air-fuel mixture is surrounded by the EGR gas, so that the stratified charge combustion in the cylinder 123 is performed not by the lean air-fuel ratio but by the stoichiometric air-fuel ratio. Since the exhaust gas during the stratified charge combustion operation is adjusted to be near the stoichiometric air-fuel ratio as described above, it has a purifying function of oxidizing hydrocarbons HC and carbon monoxide CO and reducing nitrogen oxides NOx. Purified by the three-way catalyst 115.

Further, when the load of the engine 50A increases, the amount of air passing through the intake passage 305a increases, and the E
GR gas is reduced. Then, in order to cope with a larger load, the intake control valve 306 is opened and the intake passage 1 is opened.
The cross-sectional area of 01 is increased to reduce the ventilation resistance, the fuel injection is performed in the intake stroke to promote the mixing of the intake air and the fuel, and the homogeneity in the cylinder 123A is increased, as in the first embodiment. Therefore, the stratified combustion and the homogeneous combustion by EGR are appropriately switched according to the load to operate.

8 to 10 show the operating regions on the map depending on the engine speed and the load. Figure 8
[Fig. 4] shows an operating region on a map according to the engine speed and load in the first and second embodiments. As shown, at the same engine speed,
When the engine load is small, a large amount of EG is used as compared with the intake air in order to perform stratified combustion using the EGR gas.
R gas is introduced. It can be seen that as the engine load increases, the introduction amount of the EGR gas is reduced and the homogeneous combustion is switched to.

FIG. 9 shows an operating region on a map according to the engine speed and the load in an example different from the first and second embodiments. That is, in the first and second embodiments, in order to simplify the description, “E
Although "stratified combustion using GR gas" and "homogeneous combustion" are shown, conventional stratified combustion (Fig.
As in 0), a layer due to the intake air may exist.

In other words, regarding the portion which is not the air-fuel mixture, it is considered that the air is present, the EGR gas is present, and the mixture of both is present, and the mixing ratio of the EGR gas to the air is , 0% to about 150% can be set. Moreover, the air-fuel ratio is arbitrary. However, when the mixing ratio of the EGR gas is reduced, the lean NOx catalyst is required as the configuration as in the conventional configuration, and it is necessary to perform the rich spike to deteriorate the fuel efficiency. Should be kept to the minimum time possible.

This point is taken into consideration in the map of engine speed and load in FIG. 9. For example, in an extremely low rotation or low load state including an idling state, E
Since a large amount of GR gas causes instability of combustion, the gas surrounding the air-fuel mixture is changed to air in this region. And
At medium engine speed or medium load,
As shown in the above embodiment, the air-fuel mixture is surrounded by EGR gas to perform stratified combustion at the stoichiometric air-fuel ratio. Further, in the high rotation or high load region, homogeneous combustion is performed to secure the output. In this way, it is possible to improve the fuel efficiency by suppressing the number of rich spikes as much as possible while ensuring combustion stability.

As a supplement to FIG. 9, for example, in addition to the EGR stratified combustion operation in which the air-fuel mixture is surrounded by EGR gas as described above, the stratified lean combustion operation in which the air-fuel mixture is surrounded by air and the EGR stratified combustion operation are performed. Considering that the fuel is injected in the latter half of the compression stroke during the stratified charge combustion operation near the boundary of the operation, the mixture stratification means 100 (100).
As for A), as long as the air-fuel mixture is wrapped with EGR gas, a layer of the air-fuel mixture is present near the ignition plug 113, and a layer of the EGR gas is present around the air-fuel mixture,
Further, a layer of the intake air may be present around the EGR gas, or the mixture stratification means may form the mixture layer near the ignition plug 113 as long as the mixture is wrapped with the EGR gas. In addition to the above, the intake air layer may be present around the air-fuel mixture, and the EGR gas layer may be present around the intake air. As described above, each of the embodiments of the present invention has the following functions due to the above-mentioned configuration.

That is, the engine 50 (50A) that performs stratified combustion at the stoichiometric air-fuel ratio of the first (second) embodiment is
When performing stratified charge combustion operation, the gas mixture stratification means 100
(100 A) is a forward tumble 120 (swirl 303) with intake air and a reverse tumble 121 with EGR gas.
Two tumble flows of (Swirl 304) (Swirl flow)
A flammable air-fuel mixture layer composed of fuel and intake air is present in the vicinity of the spark plug 113, and a lower intake passage that is opened and closed is provided around the air-fuel mixture via an EGR passage 109. 101 b (one intake passage 305 b) has a layer of EGR gas introduced therein, and the air-fuel mixture is wrapped with the EGR gas, whereby the cylinder 12
3 (123A), the EGR stratification combustion is performed in which the entire gas in the 123A is set to the stoichiometric air-fuel ratio instead of the lean air-fuel ratio. Therefore, the fuel consumption by reducing the pumping loss and the cooling loss by using the EGR gas is improved. In addition to improvement, for exhaust gas discharged from the cylinder 123 (123A),
Improvement of exhaust gas purification effect by performing efficient exhaust gas purification by using a three-way catalyst 115 capable of simultaneously purifying NOx, HC, etc., and system cost reduction by eliminating the need to use a lean NOx catalyst as in the conventional case, In addition, it is possible to achieve an improvement in fuel consumption by eliminating the need for the rich spike operation.

The gas mixture stratification means 100 (100A) capable of enclosing the gas mixture with the EGR gas.
As a result, the maximum flow rate of the reverse tumble 121 (swirl 304) is increased, so that the region in which stratified charge combustion operation is possible can be expanded, which also leads to an improvement in fuel consumption.

FIG. 11 compares the fuel consumption amount due to the load between the present embodiment and the prior art. First, as described above, in the prior art, stratification is performed in which the air-fuel mixture is mainly wrapped with air, whereas in the present embodiment,
Stratification is performed in which the air-fuel mixture is wrapped with EGR gas. Therefore, in the present embodiment, the specific heat ratio of the gas in the cylinder is increased in the expansion stroke of the engine, and the efficiency of the engine can be improved.

Further, in the present embodiment, the mixing of the EGR gas and the air-fuel mixture is suppressed to a necessary minimum, so that deterioration of combustion of the air-fuel mixture is prevented and combustion efficiency can be improved. Therefore, when compared with the same engine speed and load, deterioration of fuel consumption can be prevented.

As shown in the figure, in the prior art, it is necessary to apply rich spikes at regular intervals in order to maintain the activity of the lean NOx catalyst, and it is understood that the fuel consumption amount during this period is large. . On the other hand, in this embodiment, it can be seen that both the fuel consumption improvement due to the EGR and the fuel consumption improvement due to the elimination of the rich spike can be obtained.

As explained with reference to FIG. 9, when the stratified lean combustion and the stratified combustion by the stoichiometric air-fuel ratio by EGR gas are used together, the effect is obtained by the stoichiometric air-fuel ratio of the prior art and this embodiment. It is about the middle of the case of stratified combustion. As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to the embodiments and does not depart from the spirit of the invention described in the claims.
Various changes can be made in the design.

First, in the first and second embodiments, E
The basic concept of GR stratified combustion is described, and the scope of the present invention is not necessarily limited to this. For example, the number of intake passages or the number of partition walls of the passages,
Alternatively, even if the shape of the intake passage is changed, it is sufficient if the intake control valve (tumble control valve) is provided to partially close the passage and the EGR gas is introduced into the closed portion. The positions of the fuel injection valve and the ignition plug provided in the cylinder are not limited to the configuration of this embodiment, and for example, the configuration is such that fuel is injected from directly above the cylinder and ignition is performed from the side of the cylinder. The same effect as described above can be obtained in these cases as well.

Also, regarding the shape of the piston, the present invention is not necessarily restricted to this shape.
Tumbles (swirls) on the R gas side and the air-fuel mixture side exist independently of each other, and it is sufficient if the shape and structure aim to prevent mixing as much as possible until the start of combustion. In this case also, the same effect as above Can be played.

Further, although the naturally aspirated engine is described in the present embodiment, if the stratified combustion using the EGR gas can be performed, the same operation can be performed for the engine with the supercharger. In this case, since the pressure of the intake air is higher than the atmospheric pressure, the EGR
Even if gas is supplied, the amount of intake air can be increased,
The stratification operation range can be made wider than in the case of natural aspiration.

[0072]

As can be understood from the above description, the engine of the present invention that performs stratified combustion at the stoichiometric air-fuel ratio wraps the air-fuel mixture with EGR gas during the stratified combustion operation and burns at the stoichiometric air-fuel ratio. Therefore, it is possible to improve fuel efficiency and exhaust gas purification effect. In addition, in each stratified / homogeneous combustion operation, three-way catalyst works effectively to purify the exhaust gas, which further improves fuel efficiency and lowers system cost compared to using a lean NOx catalyst. Can be achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a stoichiometric air-fuel ratio stratified charge combustion engine according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram in the engine low load region in the engine of FIG.

FIG. 3 is an operation explanatory view of the engine of FIG. 1 in an engine middle load range.

FIG. 4 is an operation explanatory view of the engine of FIG. 1 in a high engine load region.

5 is an operation flowchart of the engine shown in FIG.

FIG. 6 is a piston perspective view of a stoichiometric air-fuel ratio stratified charge combustion engine according to a second embodiment of the present invention.

7 is a block diagram of the stoichiometric air-fuel ratio stratified charge combustion engine of FIG.

FIG. 8 is an operation region diagram on the map of the rotation speed and the load in FIGS. 1 and 6;

FIG. 9 is an operation region diagram on a map of a rotation speed and a load in another embodiment of the present invention.

FIG. 10 is a diagram showing an operating area on a map of a rotational speed and a load according to a conventional technique.

11 is a comparison diagram of fuel consumption amounts in FIGS. 8 to 10. FIG.

[Explanation of symbols]

50 Engine 50A Engine 100 Mixture stratification means 100A Mixture stratification means 101 Intake pipe 101a Intake passage (intake passage other than opened and closed intake passage) 101b Intake passage (intake passage opened and closed) 102 Tumble control valve (intake control Valve) 107 piston 109e EGR gas passage outlet 111 intake valve 112 exhaust valve 113 spark plug 114 partition wall 115 three-way catalyst 120 tumble flow 121 tumble flow 122 fuel injection valve 123 cylinder 123A cylinder 125 fuel spray 303 swirl flow 304 swirl flow 305a intake Passage (intake passage other than opened / closed intake passage) 305b Intake passage (opened / closed intake passage) 306 Intake control valve 305b Intake passage

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02B 31/00 301 F02B 31/00 301B 3G301 331 331A 31/02 31/02 J F02D 21/08 301 F02D 21 / 08 301C 41/02 301 41/02 301A 301E 41/04 305 41/04 305C 335 335C 43/00 301 43/00 301E 301N 301U F02M 25/07 570 F02M 25/07 570A 580 580B (72) Inventor Fujii Keiji, Hitachi, Ltd., Hitachinaka City, Oita, Takaba, 2520, Ltd., Hitachi, Ltd., Automotive Equipment Group (72) Inventor, Mamoru Fujieda, Hitachinaka, Ibaraki, Takara, Takaba, Ltd., 52, Ltd., Automotive Equipment Group, (72) Inventor, Aho Matsuharu Hitachi, Ibaraki Prefecture 2520 Takaba, Takaba, Ltd. F-term in Hitachi, Ltd. Automotive equipment group (reference) 3G023 AA05 AB03 AC05 AD07 AG01 AG03 3G062 AA07 AA08 BA04 BA05 BA06 BA08 CA07 CA08 DA01 DA02 ED04 GA04 GA06 3G084 BA09 BA15 BA20 BA21 CA03 CA04 DA02 DA10 EB08 FA07 FA10 FA33 3G091 AA11 AA12 AA17 AB03 BA14 CB02 CB03 CB05 EA01 EA03 FA13 FB11 3G092 AA06 AA17 AA18 BA04 BA05 BB06 BB19 DE03S EC09 FA21 HA04 HA11 HA21ZA21 HA21ZA21 HA21ZH21Z0712 MA01 MA19 MA29 NC02 NE13 NE14 PA01Z PE01Z PE08Z PF01Z PF03Z PF07Z

Claims (10)

[Claims] 1. An engine comprising a fuel injection valve for directly injecting fuel in a cylinder and an ignition plug for igniting a mixture of the fuel and intake air in the cylinder, the engine comprising a stratified layer. An air-fuel mixture stratification means for stratifying the air-fuel mixture during combustion operation is provided, and the air-fuel mixture stratification means forms a layer of the air-fuel mixture in the vicinity of the ignition plug so as to perform stratified combustion at a stoichiometric air-fuel ratio. An engine for stratified combustion at a stoichiometric air-fuel ratio, characterized by forming a layer of EGR gas around the air-fuel mixture. 2. The mixture stratification means includes an intake control valve for opening and closing at least one intake passage of a plurality of intake passages formed by partitioning an intake pipe, and the intake control valve is opened and closed. The engine for performing stratified combustion at the stoichiometric air-fuel ratio according to claim 1, further comprising a passage outlet of the EGR gas provided between the cylinder and the intake control valve of the intake passage. 3. The mixture stratification means generates two tumble flows in the cylinder, one of the tumble flows directing the intake air from an intake valve to an exhaust valve to a piston. 2. A flow that is directed toward the exhaust valve, and the other of the tumble flows is a flow that directs the EGR gas toward the exhaust valve along the upper surface of the piston.
Or an engine that performs stratified combustion at the stoichiometric air-fuel ratio described in 2. 4. The spray of the fuel injection valve is a deflected spray toward the spark plug, and has a penetrating force for passing through the other tumble flow and mixing with the one tumble flow. An engine that performs stratified combustion at the stoichiometric air-fuel ratio according to claim 3. 5. The mixed gas stratification means generates two swirl flows in the cylinder, one of the swirl flows being a flow of the EGR gas along a side wall surface of the cylinder. 3. The other of the swirl flows is a flow in a direction opposite to that of the one swirl flow, and is a flow for arranging the intake air inside the EGR gas. An engine that performs stratified combustion at the stoichiometric air-fuel ratio. 6. The air-fuel mixture stratification means forms a layer of the air-fuel mixture in the vicinity of the spark plug, forms a layer of the EGR gas around the air-fuel mixture, and further forms the layer of the EGR gas.
The engine for stratified combustion at a stoichiometric air-fuel ratio according to any one of claims 1 to 5, wherein a layer of the intake air is formed around a gas. 7. The air-fuel mixture stratifying means forms a layer of the air-fuel mixture in the vicinity of the spark plug, forms a layer of the intake air around the air-fuel mixture, and further forms a layer of the intake air around the air-intake. An engine for performing stratified combustion at a stoichiometric air-fuel ratio according to any one of claims 1 to 5, wherein a layer of the EGR gas is formed. 8. The fuel injection valve injects fuel in the latter half of the compression stroke during the stratified charge combustion operation, and injects the fuel during the intake stroke during the homogeneous combustion operation.
An engine that performs stratified combustion at the stoichiometric air-fuel ratio according to any one of 1 to 7. 9. An engine comprising a fuel injection valve for directly injecting fuel in a cylinder and an ignition plug for igniting a mixture of the fuel and air in the cylinder, the engine comprising stratified combustion In order to make the air-fuel ratio in the cylinder at the time of operation the stoichiometric air-fuel ratio, it is provided with a gas mixture stratification means for stratifying the air-fuel mixture, and a three-way catalyst for purifying exhaust gas at the time of the stratified combustion operation. An engine that performs stratified combustion at a stoichiometric air-fuel ratio, which is characterized by being equipped. 10. An intake control valve for opening and closing at least one intake passage among a plurality of intake passages formed by dividing an intake pipe, and the intake control valve and the cylinder for the opened and closed intake passage. An engine for stratifying and combusting the air-fuel mixture in the cylinder, comprising an air-fuel mixture stratifying means for stratifying the air-fuel mixture of fuel and intake air during stratified combustion operation having an EGR gas passage outlet therebetween. In the stratified combustion method, the intake control valve is closed to fill the EGR gas into the opened / closed intake passage, and then the intake passage other than the opened / closed intake passage is opened in an intake stroke of the engine. A flow that causes the intake air to flow into the cylinder, and a flow that causes the EGR gas to flow into the cylinder from the intake passage that is opened and closed; By injecting the fuel injection valve in the compression stroke to form a layer of the air-fuel mixture near the spark plug and a layer of the EGR gas around the air-fuel mixture, A stratified combustion method for an engine, comprising forming a stratified mixture according to a stoichiometric air-fuel ratio in a cylinder.