JPH05195879A - Exhaust gas reflux device for supercharged engine - Google Patents

Abstract

PURPOSE:To let flow back cooled EGR gas (cold EGR gas) without impairing reliability of a supercharger. CONSTITUTION:A cylinder 1 is provided with intake ports 2, 3, an exhaust port 4, and an EGR port 5, all to open toward the combustion chamber, and opening/closing valves constituted of poppet valves are arranged on the respective ports. The reflux port 15 of an EGR passage 14 communicated to the EGR port 5 is connected to a common intake passage 8 on the lower stream side of a supercharger 9. Further, a filter 17, a cooler 18, and a control valve 19 are arranged in order in the flowing direction of EGR gas on the EGR passage 14. An opening/closing valve to open/close the EGR port 5, namely, the EGR valve is opened/closed at the end stage in expansion stroke. Putting it concretely, when the pressure in the cylinder 1 is higher than the supercharging pressure, the EGR valve is opened/closed. As a result, a desired quantity of cold EGR gas is let flow back on the lower stream side of the supercharger 9 by utilizing the pressure in the cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation device for an engine with a supercharger, which has a supercharger in an intake passage and recirculates a part of exhaust gas to the engine.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 1-285651 discloses a technique in which exhaust gas (EGR gas) taken from the downstream side of a catalyst converter is recirculated to the upstream side of a supercharger. According to this, there is an advantage that a large amount of EGR can be performed in the supercharging region where the supercharger exhibits its supercharging ability.

Further, the publication discloses that a cooler is arranged in the EGR passage through which the EGR gas passes and the EGR gas is cooled by the cooler. According to this, the cold EGR gas (cold EGR) can lower the exhaust gas temperature particularly in a high load operation region, and when it is desired to increase the compression ratio of the engine and / or in the supercharger. There is an advantage that it is possible to prevent thermal damage to the exhaust system parts (particularly the catalyst converter) when it is desired to increase the generated supercharging pressure.

[0004]

However, the EGR
When a cooler is installed in the passage, this cooler allows EGR
Condensed water generated as the gas is cooled, and EG
There is a problem that coagulation is generated by fusion of carbon and the like mixed in R gas, and EGR gas containing the coagulation is recirculated to the intake passage. Of course, when the above-mentioned adhered matter enters the intake passage, the adhered matter enters the supercharger, which may impair the reliability of the supercharger.

Therefore, an object of the present invention is to provide an engine equipped with a supercharger engine without reducing the reliability of the supercharger.
It is an object of the present invention to provide an exhaust gas recirculation device for a supercharged engine that performs cold EGR.

[0006]

In order to achieve the technical problem, the present invention adopts the following constitution. That is, the intake port for EGR gas is opened to the combustion chamber of the engine, and the recirculation port for EGR gas is provided to the EGR passage connected to the intake passage on the downstream side of the supercharger and the intake port for EGR gas. And an on-off valve that is opened and closed at the end of the expansion stroke.

[0007]

The EGR gas is recirculated by the pressure difference between the exhaust pressure and the intake pressure. Therefore, when the EGR passage is connected to the intake passage downstream of the supercharger, it is generally difficult to recirculate the EGR gas. That is, when the turbocharger is used as the supercharger, although the exhaust pressure is larger than the supercharging pressure (exhaust pressure> supercharging pressure), the difference is small, and therefore a large amount of EGR gas is generated. It is difficult to recycle. On the other hand, when the mechanical supercharger is adopted as the supercharger, the exhaust pressure is smaller than the supercharge pressure (exhaust pressure <supercharge pressure), and therefore the EGR gas cannot be recirculated.

On the other hand, in the present invention, because of the above-mentioned configuration, the EGR can be performed downstream of the supercharger by utilizing the cylinder pressure at the end of the expansion stroke. On the other hand, since the timing at which the on-off valve is opened and closed is the end of the expansion stroke, the effect on the work that the engine should do is small (the work loss is small). Further, since the intake port of the EGR gas is directly opened to the combustion chamber, it is easy to cool the EGR gas by the cooling water passage existing around the combustion chamber.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 showing a part of a water-cooled multi-cylinder engine
In the figure, 1 is a cylinder, and the cylinder 1 has two intake ports 2 and 3 and one exhaust port in its combustion chamber (not shown).
The port 4 and one EGR port 5 are opened, and each of these ports 2 to 5 is provided with an on-off valve (not shown) constituted by a poppet valve.

That is, as is known, the intake port 2,
3 is provided with an intake valve, and exhaust port 4 is provided with an exhaust valve. The intake valve and the exhaust valve are opened and closed at a predetermined timing in synchronization with the rotation of the engine output shaft. ..
Similarly, an EGR valve is provided in the EGR port 5,
This EGR valve is also opened / closed at a timing described later in synchronization with the rotation of the engine output shaft.

The intake system 6 connected to the intake ports 2 and 3 will be described. The intake system 6 has a surge tank 7 as an intake expansion chamber, and the upstream side of the surge tank 7 is a common intake passage 8. The common intake passage 8 is provided with a supercharger 9 which is mechanically driven by an engine output shaft, in addition to an air cleaner, a throttle valve, etc., which are not shown. On the other hand, each cylinder 1 and the surge tank 7 are communicated with each other through an independent intake passage 10.

In the exhaust passage 11 connected to the exhaust port 4, as is known, a catalyst converter (not shown) is also used.
And a silencer are provided.

EGR passage 1 connected to the EGR port 5
Reference numeral 4 denotes an in-head EG in a cylinder head (not shown).
It is composed of an R passage 14a and an external EGR passage 14b formed of an external conduit, and its recirculation port 15 is connected to the common intake passage 8 on the downstream side of the supercharger 9. And
In the external EGR passage 14b, a filter 17 for removing solid components mixed in the EGR gas and a cooler 1 forcibly cooling the EGR gas are sequentially provided in the flow direction of the EGR gas.
8. A control valve 19 is provided, and the control valve 19 is opened and closed by an actuator 20 controlled by a signal from a control unit (not shown).

The opening / closing timing of the EGR valve arranged in the EGR port 5 will be described. The EGR valve is opened / closed at the end of the expansion stroke as shown in FIG. More specifically, when the in-cylinder pressure in the cylinder 1 is larger than the supercharging pressure, the opening / closing is performed. The amount of EGR gas recirculated to the intake system 6 by opening / closing the EGR valve is finally controlled by the control valve 15.

With the above configuration, a desired amount of EGR gas can be recirculated to the downstream side of the supercharger 9 by utilizing the in-cylinder pressure. Therefore, the reliability of the supercharger 9 is not impaired as the EGR gas is recirculated. The filter 17 may be composed of a catalyst. According to this, it becomes possible to promote the combustion of carbon or the like adhering to the filter 17 by a catalytic action, and the filter 17 can be provided with a self-cleaning function. In addition, the cooler 1
8 may be water-cooled or air-cooled.

3 and subsequent drawings show other embodiments of the present invention. In each of these embodiments, the same elements as those in the first embodiment are designated by the same reference numerals and the description thereof is omitted. It is omitted, and the characteristic part of each embodiment will be described below.

Second Embodiment (FIG. 3) In this embodiment, the EGR passage 14 is composed of an in-head passage 14a formed in a cylinder head (not shown) ,
A cooling water passage (not shown) is arranged around the in-head passage 14a. Further, fins 22 projecting toward the cooling water passage are provided around the in-head passage 14a. According to this, the EGR gas passing through the EGR passage 14 is forcibly cooled by the engine cooling water passing through the cooling water passage. The opening / closing timing of the EGR valve arranged in the EGR port 5 is the same as in the first embodiment (see FIG. 2).

Third Embodiment (FIG. 4) In this embodiment, the intake port 2 is used to perform EGR. Explaining in detail with reference to FIG. 4, the cylinder 1 is a 4-valve type with two intake valves and two exhaust valves.
The independent intake passage 10 has a first independent intake passage 10a connected to one intake port 2 (opened and closed by a first intake valve) and another intake port 3 (opened and closed by a second intake valve). The second in a row
It is partitioned into an independent intake passage 10b. And the second
The independent intake passage 10b is provided with a shutter valve 25 which is closed in a low rotation region and opened in a high rotation region. Further, the second independent intake passage 10b is provided with a shutter valve 25 toward the surrounding cooling water passage. A protruding fin 22 is provided. On the other hand, in the first independent intake passage 10a, a fuel injection valve 26 is arranged toward the one intake port 2. In the above mechanical structure, the second intake valve arranged in the other intake port 3 is opened / closed twice in each cycle, and the first opening / closing operation is performed by the EGR valve shown in FIG. The second opening / closing operation is performed at the same timing as the opening / closing timing of (1), and the second opening / closing operation is performed at the normal intake valve timing (intake stroke: broken line shown in FIG. 2).

According to the above construction, the burned gas in the cylinder 1 is transferred to the second independent intake passage by the first opening / closing operation of the second intake valve arranged in the other intake port 3. After entering the cylinder 10b and being cooled in the second independent intake passage, the cylinder 1 is again supplied in the intake stroke (second opening / closing operation of the intake valve). The burned gas in the cylinder 1 is taken into the second independent intake passage 10b, not the first independent intake passage 10a (one intake port 2) in which the fuel injection valve 26 is arranged. Therefore, it is possible to prevent the air-fuel mixture from being ignited in the independent intake passage 10b as the burned gas flows in. In other words, when the burned gas is recirculated to the first independent intake passage 10a (the one intake port 2) in which the fuel injection valve 26 is arranged, the burned gas that has flowed into the first independent intake passage 10a is recirculated. The heat of the gas may cause the fuel discharged from the fuel injection valve 26 to burn in the first independent intake passage 10a.

Fourth Embodiment (FIGS. 5 to 7) This embodiment is a modification of the third embodiment (FIG. 4). That is, in a four-cylinder engine in which four cylinders 1 are arranged, the EGR is performed in the independent intake passage 10b by utilizing the cylinder internal pressure in another cylinder 1. The details will be described below. In FIG. 5, the ignition sequence of the 4-cylinder engine is as follows: No. 1 cylinder (No. 1), No. 3 cylinder (No. 3),
The order of the fourth cylinder (No. 4) and the second cylinder (No. 2) is set. Assuming this ignition sequence, the first cylinder (N
o. Independent intake passage 10 between No. 1) and No. 4 cylinder (No. 4)
b are communicated with each other via the communication passage 30A, and the third cylinder (N
o. 3) and the independent intake passage 10 between the second cylinder (No. 2)
b are communicated with each other via a communication passage 30B. The communication passages 30A and 30B are formed in a cylinder head (not shown), and the communication passages 30A and 30B are provided with fins 22 protruding toward the cooling water passages around them.

The second intake port 3 is provided in the other intake port 3.
The intake valve is, as shown in FIG. 6, the same as in the third embodiment.
The opening / closing operation is performed twice in each cycle, the first opening / closing operation is opened / closed at the same timing as the opening / closing timing of the EGR valve shown in FIG. 2, and the second opening / closing operation is performed at the normal intake valve timing (intake Process: It is opened and closed by the broken line shown in FIG.

The operation of the above-described structure will be described with reference to FIG. It is returned to the fourth cylinder (No. 4) having the intake stroke at the same timing through the communication passage 30A. Then, the EGR gas is cooled in the process of passing through the communication passage 30A, so that the cooled EGR gas is recirculated to the fourth cylinder (No. 4).

Similarly, the EGR gas that has entered the independent intake passage 10b by the first opening / closing of the second intake valve in the third cylinder (No. 3) passes through the communication passage 30B and is indicated by the arrow in FIG. Then, at the same timing, it is recirculated to the second cylinder (No. 2) which is in the intake stroke. In addition, the fourth cylinder (No.
The EGR gas that has entered the independent intake passage 10b due to the first opening / closing of the second intake valve in 4) passes through the communication passage 30A and is in the intake stroke at the same timing in the first cylinder (N).
o. It is refluxed to 1). In addition, the second intake valve in the second cylinder (No. 2) is opened and closed for the first time so that the independent intake passage 10
The EGR gas that has entered the b is recirculated to the third cylinder (No. 3) having the intake stroke at the same timing through the communication passage 30B.

Similarly, in the case of a six-cylinder engine having six cylinders 1, for example, the ignition order is, for example, the first cylinder (No. 1), the second cylinder (No. 2), and the third cylinder.
No. 3 cylinder (No. 3), No. 4 cylinder (No. 4), No. 5 cylinder (No. 5), No. 6 cylinder (No. 6),
As shown by the arrow in FIG. 7, it suffices that the independent intake passages 10b of the first cylinder and the fourth cylinder communicate with each other.
The independent intake passages 10b of the No. cylinder and the independent intake passages 10b of the No. 3 cylinder and the No. 6 cylinder may be made to communicate with each other.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments and includes the following modifications. (1) The supercharger 9 is not limited to a mechanical supercharger, and may be a turbocharger driven by exhaust energy. (2) For example, in the first embodiment, the EGR return port 15 is connected to the common intake passage 8, but the EGR return port 15 may be connected to the independent intake passage 10.

[0027]

As is apparent from the above description, according to the present invention, a desired amount of EGR gas can be recirculated to the downstream side of the supercharger by utilizing the in-cylinder pressure. Does not impair the credibility of. Further, since the in-cylinder pressure at the end of the expansion stroke is used, the work loss of the engine is small. Further, since the intake port of the EGR gas is open to the combustion chamber, it is easy to forcibly cool the EGR gas by the engine cooling water passing through the cooling water passage existing around the combustion chamber.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an EGR device according to a first embodiment.

FIG. 2 is an EGR opening into a combustion chamber in the first embodiment.
The figure which shows the relationship between the opening / closing timing of the EGR valve which opens and closes a gas inlet, and cylinder pressure.

FIG. 3 is a schematic diagram of an EGR device according to a second embodiment.

FIG. 4 is a schematic diagram of an EGR device according to a third embodiment.

FIG. 5 is a schematic diagram of an EGR device according to a fourth embodiment.

FIG. 6 is an operation explanatory view in the case of a four-cylinder engine in the fourth embodiment.

FIG. 7 is an operation explanatory view of a 6-cylinder engine in the fourth embodiment.

[Explanation of symbols]

 1 cylinder 2 1st intake port 3 2nd intake port 4 exhaust port 5 EGR port 6 intake system 8 common intake passage 9 supercharger 10 independent intake passage 10a connected to the first intake port Independent intake passage 10b Independent intake passage connected to the second intake port 14 EGR passage 14a In-cylinder head EGR passage 14b External EGR conduit 15 EGR recirculation port 26 Fuel injection valve 30A, 30B Communication passage

Claims (10)

[Claims] 1. An EGR passage in which an intake port for EGR gas is opened to a combustion chamber of an engine, and a return port for EGR gas is connected to an intake passage downstream of a supercharger; An exhaust gas recirculation device for an engine with a supercharger, comprising: an opening / closing valve which is disposed at a mouth and is opened / closed at the end of an expansion stroke. 2. The engine with a supercharger according to claim 1, wherein the on-off valve is opened and closed at the end of the expansion stroke and when the in-cylinder pressure is higher than the supercharging pressure. Exhaust gas recirculation device. 3. The exhaust gas recirculation system for an engine with a supercharger according to claim 2, wherein the EGR passage is constituted by an external conduit. 4. The exhaust gas recirculation device for an engine with a supercharger according to claim 3, wherein an EGR cooler for cooling EGR gas is provided in the external conduit. 5. The EGR passage according to claim 2, wherein at least a part of the EGR passage is formed inside the cylinder head, and the EGR passage is arranged adjacent to the cooling water passage in the cylinder head. Exhaust gas recirculation system for supercharged engines. 6. The supercharger according to claim 5, wherein the EGR passage formed inside the cylinder head is provided with a fin projecting toward the cooling water passage. Exhaust gas recirculation system for engines. 7. The intake port according to claim 1, wherein the intake port for the EGR gas is open to the combustion chamber.
An exhaust gas recirculation system for an engine with a supercharger, characterized in that an intake valve that is configured by a port and that opens and closes the intake port constitutes the on-off valve. 8. The fuel injection valve according to claim 7, wherein a fuel injection valve is provided in one of the two intake ports open to the combustion chamber, and the other intake port is the aforementioned intake port. An exhaust gas recirculation system for an engine with a supercharger, which constitutes an intake port for EGR gas. 9. The engine with a supercharger according to claim 7, wherein the engine with a supercharger is a multi-cylinder engine, and among the intake ports constituting the intake port of the EGR gas of each cylinder, the end of the expansion stroke and the intake An exhaust gas recirculation system for a supercharged engine, comprising: a communication passage that communicates intake ports of cylinders whose strokes overlap each other. 10. The communication passage according to claim 9, wherein the communication passage is formed inside the cylinder head, and is arranged adjacent to the cooling water passage in the cylinder head.
An exhaust gas recirculation device for an engine with a supercharger, which is characterized in that