JPH07103080A - Egr device for automobile engine - Google Patents

Abstract

PURPOSE:To provide an EGR device which effectively utilizes a two-intake valve type intake form to promote the mixing of circulating EGR gas, and uniforms the distribution of EGR-rate in a cylinder to stabilize combustion even at the time of engine operation where a large quantity of EGR gas is circulated. CONSTITUTION:In each cylinder, the tip of an intake manifold is branchingly formed, and a control valve 10 to control the quantity of intake air is arrangedly provided in the first branch passage 8a on one side, and the outlet of an independent ERG pipe line 15 is connected to the second branch passage 8b on the other side, and each branch passage communicates severally with the first and the second intake port 13a, 13b formed in a cylinder head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile engine E.
The present invention relates to a GR device, and more particularly to an EGR device that is a two-valve intake valve and is most suitable for a cylinder direct injection engine that directly injects fuel into a cylinder.

[0002]

2. Description of the Related Art As one means for reducing NOx in the exhaust gas of an automobile engine, a part of the exhaust gas is recirculated to an intake system and mixed in an intake air mixture to lower the maximum temperature during combustion to reduce NOx. To reduce the occurrence of
R device) is well known in the art. There are two methods of returning the EGR gas to the intake system: returning to the upstream of the throttle valve (upstream EGR) and returning to the downstream of the throttle valve (downstream EGR).
As an example of R, the prior art described in JP-A-55-49565 is conventionally known.

In the above-mentioned prior art, as shown in FIG. 5, an intake passage a and an EGR passage b are constituted by independent passages, and fresh air passing through the intake passage a is intake valve a1. Is introduced into the cylinder c through the EGR passage b, and the EGR gas passing through the EGR passage b is introduced into the cylinder c through the intake valve b1. In this case, in the above-mentioned prior art, EG
As for the valve timing of the intake valve b1 on the R gas side,
By setting the valve timing of the intake valve a1 on the fresh air side earlier than the valve opening timing, the fresh air and EGR gas are stratified. On the upstream side of the EGR passage b,
An EGR control valve d is provided to control the flow rate of EGR gas according to the load of the engine, and the EGR gas is cut off when the load is high.

[0004]

In the above-mentioned prior art, however, a single cylinder c has two intake passages, one of which is for fresh air and the other is for EGR gas. However, since the EGR gas passing through the passage b cuts off the recirculation at a high load according to the load of the engine, it cannot be said that it is necessarily advantageous in all operating conditions of the engine in terms of the output of the engine. Especially, in the high load region, the charging efficiency of intake air becomes low, so that the advantage of using the two-valve intake system instead of the complicated structure of the two-valve intake system cannot be fully utilized.

The present invention intends to promote the mixing of the EGR gas that recirculates by effectively utilizing the intake type of the two-valve intake type.
An object of the present invention is to provide an EGR device capable of stabilizing combustion even during engine operation in which a large amount of EGR gas is recirculated by uniformizing the EGR rate distribution in the cylinders.

[0006]

As means for achieving this object, the present invention provides that the intake port of each cylinder is formed as a two-valve independent first intake port and second intake port.
For each cylinder, a control valve for controlling the intake air amount is arranged on the side of the first intake port on one side of the cylinder, and under the engine operating condition in which the control valve is closed in the EGR recirculation region, the other control valve The flow rate of the intake air flow that is drawn into the cylinder through the two intake ports is increased, and the outlet of the EGR pipe line that is independently piped for each cylinder is provided on the second intake port side of each cylinder. Each of them is independently connected, and the EGR pipe is provided with an EGR control valve for controlling the opening and closing of the passage in the middle of the passage. Also, the second intake port is formed as a helical port.

[0007]

In the EGR device having the above-mentioned structure, since the independent EGR pipes are separately connected to the second intake port side of each cylinder, the EGR gas recirculated to the intake system is It becomes difficult to be affected by intake air pulsation in the inside, blowback of intake air, etc. As a result, the distribution of EGR gas to each cylinder is made uniform.

The EGR gas introduced into each cylinder is E
Since it is introduced to the side of the second intake port where the flow velocity of the intake flow increases in the GR recirculation region (at low and medium speeds and at low and medium loads), the EGR gas flowing into the cylinder is not mixed with fresh air. As a result, swirls are generated in the cylinder, and the mixing effect described above is maintained for a long time until the first half of the compression stroke. As a result, the EGR rate distribution in the cylinder is made uniform, and efficient NOx emission reduction is realized.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a schematic plan view of an intake system of a horizontally opposed four-cylinder engine to which an EGR device according to the present invention is applied, and FIG. 2 is a front view of FIG. 1 and 2, reference numeral 1 is a cylinder block, reference numeral 2 is a cylinder head 2 connected to the left and right of the cylinder block 1, and the cylinder block 1 has cylinders 3 and 4, respectively, as seen in a normal engine. ,
Cylinders 5 and 6 are provided. An intake manifold 8 is arranged in parallel from an intake collecting portion 7 arranged at the center so as to communicate with the intake ports of each cylinder of the cylinder heads 2 arranged on the left and right of the cylinder block 1. The manifold 8 has its tip branched to form a first branch passage 8a and a second branch passage 8b. Further, an intake passage 9 having a throttle valve (not shown) is connected to the central intake collecting portion 7.

In the present invention, as shown in FIGS. 1 and 2, of the first branch passage 8a and the second branch passage 8b, the intake air amount is placed in the first branch passage 8a on one side. A control valve 10 is provided to control the. The control valve 10 is configured to be controlled by an electronic control unit provided in the engine. For example, when a large amount of EGR gas is recirculated based on a detection signal of the throttle opening, such as during low load operation, the valve is opened. Is fully closed, and during high-load operation, the EGR control valve described later cuts off the recirculation of EGR gas. In this case, since a large amount of fresh air is required, the valve opening should be fully opened. It is controlled to do so.

By providing the control valve 10 in the first branch passage 8a on one side, in the engine operating state in which the control valve 10 is controlled to be closed, the control valve 10 is introduced into the cylinder via the other second branch passage 8b. The flow velocity of the inhaled intake air flow increases. Therefore, in the present invention, the EGR pipe 15 is provided in the second branch passage 8b of each of the above-described cylinders 3 to 6.
The outlets 15a are communicated with each other. Here, the EGR pipe line 15 has an upstream end 15b as shown in FIG.
Is connected to the exhaust system, and an EGR control roll valve 16 for controlling the opening / closing of the passage to control the recirculation amount of EGR gas is provided in the middle of the pipeline.
6 is branched from the position of the intake collecting portion 7 to the left and right, and each of the conduits extends to the left and right along the space between the intake manifolds 8 arranged in parallel, and the tip is branched into two. The outlets 15a formed at the ends of the respective branch pipes,
For each cylinder, the second branch passage 8b of each cylinder is separately communicated.

FIG. 3 is an enlarged plan view showing the periphery of a single cylinder combustion chamber. In each of the cylinders 3 to 6, two intake valves 11a and 11b and two exhaust valves 12a and 12b are arranged in parallel for a single cylinder as shown in an enlarged view in FIG. It has a four-valve type valve configuration. The two intake valves 11a and 11b arranged in a single cylinder (the cylinder 4 in the left column is shown as an example in FIG. 1) are formed in the cylinder head 2 with the respective intake valves arranged. A first intake port 13a and a second intake port 13b, and these intake ports 13a, 13b are branched passages 8a, 8 formed at the tip of the intake manifold 8.
It is connected to b. From that, the intake manifold 8
The intake flow introduced into the cylinder 4 via the shunt is divided into the first intake port 13a and the second intake port 13b, and is sucked into the combustion chamber in the cylinder 4. Further, the exhaust valves 12a and 12b provided in the cylinder 4 are configured so that two exhaust ports 14a and 14b in which the respective exhaust valves are arranged are collected and discharged from a single exhaust passage 14c. The above-mentioned configuration is the same for other cylinders.

Next, the operation of the present invention will be described. In the present invention, as shown in FIGS. 1 and 2, the front end of the intake manifold 8 is branched for each cylinder, and the first branch passage 8 on one side thereof is formed.
A control valve 10 for controlling the intake air amount is provided in a, and an outlet 15a of an independent EGR pipe 15 is separately connected to the other second branch passage 8b, and each branch passage is provided in the cylinder head 2. The first intake port 13a and the second intake port 13b that are formed are communicated with each other. With the above configuration, since the control valve 10 is closed in the EGR recirculation region (at low and medium speeds and low and medium loads), there is no intake of fresh air from the first intake port 13a in each cylinder, and there is no intake of the second intake air. It is inhaled only from the port 13b. Therefore, the flow rates of the EGR gas and the fresh air gas that flow into the respective cylinders from the second intake port 13b increase, and the swirls occur because they flow into the respective cylinders, and mixing of the EGR gas and the fresh air is promoted. . The mixing of EGR gas and fresh air is continued until the intake stroke and the compression stroke.
As a result, the EGR rate distribution in the cylinder becomes uniform. Further, the strength of the swirl generated is weak to medium (swirl ratio 1 because the cross-sectional area of the intake port 13b is not narrowed).
~ 2), and decays in the latter half of the compression stroke.

Further, in the present invention, as shown in FIG.
The second intake port 13b in the helical port 13
It may be changed to b ′, and swirl is generated more reliably in the cylinder than swirl generation only by increasing the inflow speed. Especially E
Fresh air and EG flowing into the cylinder from the helical port 13b ′ in the GR recirculation region (at low and medium speeds and at low and medium loads)
As described above, the R gas produces a weak to medium swirl (swirl ratio 1 to 2) in the cylinder, and sufficiently mixes the fresh air and the EGR gas. Then, as in the case of the straight second intake port 13b, the mixing effect is maintained for a long period until the beginning of the compression stroke, and the EGR rate distribution in the cylinder is made uniform.

Further, in the above-described embodiment, E is provided in the second branch passage 8b formed by the branch of the intake manifold 8.
The outlets 15a of the GR conduit 15 are connected to each other, but the present invention is not limited to this, and even if the outlet 15a of the EGR conduit 15 is connected to the second intake port 13b formed in the cylinder head 2. Good.

[0016]

As described above, according to the present invention, since an independent EGR pipe is connected to the second intake port side of each cylinder, the EG recirculated to the intake system.
The R gas is less likely to be affected by intake pulsation in the intake passage, blowback of the intake air, etc. As a result, the distribution of the EGR gas to each cylinder is made uniform. Further, since the EGR pipe line is connected to the side of the second intake port where the flow velocity increases in the EGR recirculation region, mixing of the EGR gas flowing into the cylinder with fresh air is promoted, and swirl is also generated in the cylinder to cause the above problem. The mixing effect of is enhanced. Therefore, even in a large amount of EGR recirculation region, the EGR rate distribution in the cylinder becomes uniform, and there is no portion with an extremely high EGR rate, so combustion is stabilized and a large amount of exhaust gas can be recirculated. Therefore, low fuel consumption and low NOx value are realized.

[Brief description of drawings]

FIG. 1 is a schematic plan view of an intake system of a horizontally opposed four-cylinder engine.

FIG. 2 is a schematic front view of an intake system of a horizontally opposed four-cylinder engine.

FIG. 3 is a plan view around the combustion chamber of a single cylinder.

FIG. 4 is a plan view around a combustion chamber of a single cylinder.

FIG. 5 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 1 Cylinder Block 2 Cylinder Head 3 Cylinder 4 Cylinder 5 Cylinder 6 Cylinder 7 Intake Collecting Section 8 Intake Manifold 8a First Branch Passage 8b Second Branch Passage 9 Intake Passage 10 Control Valve 11a Intake Valve 11b Intake Valve 12a Exhaust Valve 12b Exhaust Valve 13a First intake port 13b Second intake port 14a Exhaust port 14b Exhaust port 14c Exhaust passage 15 EGR pipe 15a Outlet 16 EGR control valve

Claims (2)

[Claims] 1. An intake port of each cylinder is formed of a two-valve independent first intake port and a second intake port, and intake air is provided on one side of the first intake port for each cylinder. Under engine operating conditions in which a control valve for controlling the amount is arranged and the control valve is controlled to be closed in the EGR recirculation region, the flow velocity of the intake flow sucked into the cylinder via the other second intake port increases. On the side of the second intake port of each cylinder, the outlet of the EGR pipe line independently piped is connected to each cylinder independently, and the EGR pipe line is connected to the outlet in the middle thereof. An EGR device for an automobile engine, comprising an EGR control valve for controlling opening and closing. 2. The EGR device for an automobile engine according to claim 1, wherein the second intake port is formed as a helical port.