JPH11148429A - Exhaust gas recirculation device - Google Patents

Abstract

(57) Abstract: In an internal combustion engine having a plurality of intake ports, a swirl flow is formed concentrically in the combustion chamber by each intake port, and intake air having a different EGR gas amount is supplied depending on operating conditions to supply the combustion chamber. The present invention provides an exhaust gas recirculation device which controls an exhaust gas recirculation layer formed in the exhaust gas recirculation device to achieve low NOx, low PM, and low fuel consumption. A plurality of intake ports (3, 4) and intake manifolds (11, 12) are independently provided in a combustion chamber (8) of an internal combustion engine (1), and a swirl flow is concentrically formed in the combustion chamber (8) by the intake ports (3, 4). The exhaust gas recirculation control valves 25 and 26 are switched according to the operating conditions to control an exhaust gas recirculation layer (EGR layer) formed in the combustion chamber 8 and the amount of exhaust gas recirculated into the combustion chamber 8. Is controlled to an optimal value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an exhaust gas recirculation device.

[0002]

2. Description of the Related Art In an internal combustion engine, a part of burned exhaust gas is mixed into intake air to slow down combustion to lower combustion temperature and reduce nitrogen oxides (hereinafter referred to as "NOx"). As a recirculation (EGR) device, a sub-port is provided for an intake port of a direct injection diesel engine, and exhaust gas is introduced to this sub-port (hereinafter referred to as “EG”).
R gas), an exhaust gas recirculation device (JP-A-1-180618) that collects EGR gas near the nozzle (at the center) to improve exhaust gas characteristics and durability.
A sub port for forming a swirl flow near the center is provided at an intake port of a stratified combustion engine of a spark ignition type, and the sub port (flow toward the center) is supplied with intake air without EGR gas, and a main port (outer periphery) is provided. Exhaust gas recirculation device (Japanese Patent Laid-Open No.
-89659).

[0003]

However, in the above-described sub-port type, it is difficult to form a swirl flow which is not entrained in the flow by the main port.
Mixing of R gas and fresh air is unavoidable, and efficient layered E
GR distribution cannot be obtained. Since the size of the sub port is limited, the EGR gas is limited to a small amount, and a high EGR rate cannot be obtained. If the sub port is made large, the swirl flow becomes weak, and there is a concern that smoke and HC will increase. In a multi-valve (three-valve or four-valve) engine having two intake valves, the space between the intake ports and valves is narrow, so that the internal structure of the cylinder head is complicated, and it is possible to manufacture a cylinder head provided with a sub port. Very difficult. Therefore, there is a problem that it cannot be applied to a multi-valve engine having high potential such as high output and low exhaust gas.

Therefore, according to the present invention, in an internal combustion engine having a plurality of intake ports, a swirl flow is formed concentrically in the combustion chamber by each intake port, and intake air having a different amount of EGR gas is supplied depending on operating conditions to perform combustion. An object of the present invention is to provide an exhaust gas recirculation device that controls an exhaust gas recirculation layer formed in a room to achieve low NOx, low PM (smoke, HC), and low fuel consumption.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of intake ports and an intake manifold are independently provided in a combustion chamber of an internal combustion engine. A swirl flow is formed concentrically, and each exhaust gas recirculation control valve is switched according to the operating conditions of the internal combustion engine. This controls the exhaust gas recirculation layer formed in the combustion chamber and controls the amount of exhaust gas recirculated into the combustion chamber to an optimal value.

According to the second aspect of the present invention, a swirl flow is formed along the center of the combustion chamber by the intake port on the upstream side of the swirl flow, and the swirl flows toward the wall surface of the combustion chamber by the intake port on the downstream side of the swirl flow. Form a flow. Thereby, the swirl flow is formed concentrically, and an ideal stratified EGR gas distribution can be obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. FIG. 1 shows a schematic configuration diagram of an exhaust gas recirculation device as an embodiment of the present invention. In FIG. 1, an engine 1 as an internal combustion engine is a multi-cylinder engine, for example, a multi-valve (four-valve) engine having two intake valves and two exhaust valves per cylinder, and a cylinder head 2.
Are provided with two intake ports 3, 4 and two exhaust ports 5, 6 for each cylinder. Further, as shown in FIG. 2, a cylinder 8 forming a lower part of the combustion chamber is formed in the cylinder block 7. The intake port 3 is connected to the intake manifold 15 through the intake passage 11 and the intake port 4.
Are connected to an intake manifold 16 through an intake passage 12. The exhaust ports 5 and 6 are connected to an exhaust manifold 17. In addition, the intake manifold 5,
6 may be provided independently as shown, or 1
The inside of one manifold may be divided by a partition. FIG. 1 shows only one cylinder.

The intake manifolds 15 and 16 are connected to an air cleaner 22 via intake passages 20 and 21, respectively, and are connected to an exhaust manifold 17 via exhaust gas recirculation passages (hereinafter referred to as "EGR passages") 23 and 24, respectively. Have been. Exhaust gas recirculation control valves (hereinafter, referred to as “EGR valves”) 25 and 26 are provided in the EGR passages 23 and 24. The EGR passage 2 is provided in the intake passages 20 and 21.
The intake throttle valves 27 and 28 are connected to the upstream side (closer to the air cleaner 22) of the junction with the air inlets 3 and 24. These EGR valves 25 and 26 and intake throttle valves 27 and 28
It is controlled by an electronic control unit (ECU) 30 according to the operating conditions of the engine 1.

As shown in FIGS. 2 and 3, the intake port 3,
The direction of each swirl flow formed by the swirl flow 4 is, for example, counterclockwise as shown by a dotted arrow A and a solid line arrow B, and the intake port 3 is located on the upstream side of the swirl flow, The port 4 is arranged so as to be located downstream of the swirl flow. The intake port 3 is formed so that the swirl flow is directed toward the center of the cylinder 8 and downward as shown by an arrow A in FIG.
The swirl flow is formed along the wall surface (inner peripheral surface) of the cylinder 8 as shown by the arrow B. That is, the inflow angles and the flow rates of the intake ports 3 and 4 are adjusted so that the respective flows do not interfere with each other.
Towards the center, the outflow direction of the downstream intake port 4 is
The first swirl flow A (the area indicated by oblique lines) near the center of the cylinder 8 by the intake port 3 and the second swirl flow outside the first swirl flow by the intake port 4 by being arranged along the wall surface of the cylinder 8. The flow B (the area shown in white) is formed. Thereby, two swirl flows A and B are formed concentrically in the cylinder 8.

The operation will be described below. Electronic control unit 30
Are the engine rotation sensor 31 and the accelerator opening sensor 32
The operating conditions of the engine 1 are determined based on a signal from a sensor that detects the operating state of the engine 1, such as the operation state of the engine 1, and the EGR valves 25 and 26 are respectively opened (fully opened) and partially opened (1) based on the EGR control map shown in FIG. / 2 opening), closing (fully closing), and controlling the intake throttle valves 27 and 28 to open (full opening), half opening (1/2 opening), and throttle (for example, 1/4 opening) respectively. And each EGR supplied to the intake manifolds 15 and 16
The amount of gas and the amount of fresh air are independently controlled.

That is, in the low to medium load operation range, E
The GR valve 25 is opened, the EGR valve 26 is closed, and the intake throttle valve 2 is opened.
7, the intake throttle valve 28 is opened, and EGR gas is supplied only to the vicinity of the center of the cylinder 8. In the middle to high load operation range, the EGR valves 25 and 26 are opened, and the intake throttle valve 2 is opened.
The EGR gas is supplied to both the vicinity of the center and the peripheral portion of the cylinder 8 by squeezing 7 and 28. In the high load operation region, the EGR valves 25 and 26 are closed, and the intake throttle valves 27 and 28 are closed.
To supply only fresh air to the cylinder 8. Thus, the amount of EGR gas into the cylinder 8 can be adjusted over a wide range, and can be controlled to an optimum value.

For example, in the combustion of a direct injection diesel engine, premixed combustion (combustion of fuel injected during the period from fuel injection to ignition) has a high combustion temperature and a large amount of NOx. Therefore, by applying the exhaust gas recirculation device of the present invention to form a region where the EGR gas is rich near the center of the cylinder 8 and a region where the EGR gas is thin (a lot of fresh air) around the cylinder 8, HC and smoke are reduced. Effectively reduce NOx by minimizing generation.

That is, since the spray is distributed in a region where the EGR rate is high in the early stage of the injection, the period until ignition (ignition delay) is prolonged, and the proportion of premixed combustion is increased (the generation of NOx due to the high EGR rate). Is suppressed). In the diffusion combustion region, combustion is performed in a region where the EGR gas is thin (low EGR), so that unburned HC and smoke are reduced. It is preferable that the EGR rate in the vicinity of the cylinder wall is low from the viewpoint of the durability of the piston ring and the oil. In a region where the load is medium or higher, the contribution ratio of NOx generation by diffusion combustion becomes high, and depending on the operating conditions, EGR may be required in the peripheral portion in order to further improve performance. In such a case, NOx can be reduced by using an EGR control map as shown in FIG.

As described above, by supplying the intake air having different EGR rates to the vicinity of the center and the outer periphery of the cylinder 8, it becomes possible to control the amount of the EGR gas into the cylinder 8 to an optimum value. This makes it possible to simultaneously improve low PM (smoke, HC) or low fuel consumption, which are difficult to achieve. FIG. 5 shows an example of a control map of each valve in the case where the load ratio (output ratio) changes when a specific operating condition, for example, the engine speed is kept constant, in the EGR control map of FIG.

For example, when the load condition is an operating condition of 20% or less, the EGR valves 25 and 26 are opened (fully open), the intake throttle valves 27 and 28 are throttled (1/4 opening), and the intake manifolds 15 and 16 are opened. The EGR gas amount is increased and the supply amount of fresh air is reduced, so that the entire region in the cylinder 8 is set to a high EGR rate. When the load factor is in an operating condition of 20% to 40%, the EGR valve 25 is opened (fully opened), the EGR valve 26 is half-opened (1/2 opening), and the intake throttle valve 27 is throttled (1/4 opening). The intake throttle valve 28 is half-opened (1/2 opening), and the intake air distribution in the cylinder 8 is set to high EGR at the center and low EGR at the periphery. Load factor is 40
% To 60%, the EGR valve 25 is opened (fully opened), the EGR valve 26 is closed (fully closed), and the intake throttle valve 2 is opened.
7, the throttle valve 28 is opened (1/4 opening), the intake throttle valve 28 is opened (full open), and the intake air distribution in the cylinder 8 is set to high EGR only in the center and only fresh air in the periphery.

When the load factor is an operating condition of 60% to 80%, the EGR valves 25 and 26 are half-opened (1/2 opening), the intake throttle valves 27 and 28 are opened (fully open), and the intake air in the cylinder 8 is opened. The distribution is set to low EGR in the entire region. And the load factor is 80
%, The EGR valves 27 and 28 are closed (fully closed), the intake throttle valves 27 and 28 are opened (fully open), and the intake air distribution in the cylinder 8 is limited to fresh air in the entire region. In this way, intake air having different EGR rates is supplied to the vicinity of the center and the outer periphery of the cylinder 8 according to the operating conditions of the engine 1.

In the above exhaust gas recirculation system, the structure of the current engine is changed except for a slight change in the layout of the intake ports 3 and 4.
6 is a split type, and the EGR passages 23 and 24 and the EGR valve 2
5, 26, and intake throttle valves 27, 28 can be realized simply by adding them, and can be produced at lower cost compared to a sub-port type that requires a major change in the internal structure of the cylinder head. Becomes

Further, in the above-described embodiment, E is used to supply intake air having different EGR rates to the vicinity of the center and the outer periphery of the cylinder 8.
As the GR gas distribution, a case where a region with a large amount of EGR gas (high EGR ratio) is formed near the center of the cylinder 8 and a region with a large amount of fresh air (low EGR ratio) is formed on the outer peripheral portion is described. Conversely, it is possible to form a region with a large amount of EGR gas (high EGR rate) on the outer peripheral portion of the cylinder 8 and to form a region with a large amount of fresh air (low EGR ratio) near the center.

The exhaust gas recirculation device of the present invention is not limited to a direct injection type diesel engine, but can be applied to an internal combustion engine which performs stratified combustion, for example, a direct injection type spark ignition type gasoline engine. It is.

[0020]

According to the present invention, since a swirl flow can be formed concentrically in the combustion chamber, the region where the EGR gas is rich and the region where the EGR gas is thin are clearly separated, and the reduction of NOx, smoke, HC and the like can be achieved. It is planned. Further, by supplying concentrically different intake amounts of EGR gas into the combustion chamber, it is possible to control the amount of exhaust gas recirculated into the combustion chamber to an optimum distribution, and to obtain NOx, PM (smoke, H
C), it is possible to improve characteristics that are hardly compatible with each other, such as fuel efficiency. Further, it is possible to configure the exhaust gas recirculation device without largely changing the internal structure of the cylinder head, and it is possible to produce at low cost.

According to the present invention, the intake port on the upstream side of the swirl flow forms a swirl flow toward the center of the combustion chamber. Are provided so as to form a swirl flow along, so that a swirl flow can be formed concentrically, and ideal stratified EGR control can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an exhaust gas recirculation device according to the present invention.

FIG. 2 is an explanatory diagram of a swirl flow formed in a cylinder by an intake port of FIG. 1;

FIG. 3 is a side view of a swirl flow formed in the cylinder of FIG. 2;

FIG. 4 is a view showing an example of an EGR control map of the exhaust gas recirculation device of FIG. 1;

FIG. 5 is a diagram showing an example of a control map of an EGR valve and an intake throttle valve in a specific operation state of the EGR control map of FIG. 4;

[Explanation of symbols]

 Reference Signs List 1 engine (internal combustion engine) 2 cylinder head 3, 4 intake port 5, 6 exhaust port 7 cylinder block 8 cylinder (combustion chamber) 15, 16 intake manifold 20, 21 intake passage 23, 24 EGR passage (exhaust gas recirculation passage) 25 , 26 EGR valve (exhaust gas recirculation control valve) 27, 28 Intake throttle valve 30 Electronic control unit (ECU)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 21/08 301 F02D 21/08 301A 41/02 360 41/02 360

Claims (2)

[Claims] 1. An exhaust gas recirculation device that recirculates a part of exhaust gas of an internal combustion engine as recirculated gas to a combustion chamber of the internal combustion engine, wherein the exhaust gas recirculation device is provided independently of a cylinder head of the internal combustion engine and is provided in the combustion chamber. A plurality of intake ports provided concentrically to form a swirl flow; a plurality of intake manifolds independently provided so as to be connected to the respective intake ports; and exhaust gases respectively connected to the respective intake manifolds. An exhaust gas formed in the combustion chamber, comprising: a gas recirculation passage; and an exhaust gas recirculation control valve provided in each of the exhaust gas recirculation passages, wherein each of the exhaust gas recirculation control valves is switched according to operating conditions of the internal combustion engine. An exhaust gas recirculation device characterized by controlling a recirculation layer. 2. An intake port on the upstream side of the swirl flow out of the plurality of intake ports is provided so as to form a swirl flow toward the center of the combustion chamber, and the intake port on the downstream side of the swirl flow is The swirl flow is formed along the wall surface of the combustion chamber.
An exhaust gas recirculation device according to any one of the preceding claims.