JP3392733B2 - Exhaust recirculation system for internal combustion engine - Google Patents

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 returning a part of exhaust gas to a combustion chamber in an internal combustion engine.

[0002]

2. Description of the Related Art FIG. 6 shows a typical exhaust gas recirculation system (hereinafter referred to as E
FIG. 1 is a system diagram of an internal combustion engine including a GR device). In the figure, 1 is a piston, 9 is a cylinder, 40 is a combustion chamber formed by the upper surface of the piston 1 and the inner surface of the cylinder 9, 3 is an intake valve, 6 is an exhaust valve, 2 is an intake pipe, 8 is an exhaust pipe. , 20 are fuel injection valves for injecting fuel into the combustion chamber 40. Reference numeral 7 denotes an EGR passage (exhaust gas recirculation passage) branched from the exhaust pipe 8 and connected to the intake pipe 2, 4 an EGR valve for opening / closing the EGR passage 7, and 5 EGR for controlling the opening / closing of the EGR valve 4. It is a valve controller.

During operation of an internal combustion engine equipped with such an EGR device, combustion in the combustion chamber 40 ends and the piston 1
The exhaust valve 6 opens in the early stage of the rise of the exhaust gas, and the exhaust gas flows into the exhaust pipe 8. Engine controller (not shown)
When the EGR valve opening control signal is input to the EGR valve controller 5, the EGR valve 4 opens. When the EGR valve 4 is opened, the exhaust pipe 8 and the intake pipe 2 are communicated with each other by the EGR passage 7, and when the pressure of the exhaust gas in the exhaust pipe 8 is higher than the pressure of the air (intake) in the intake pipe 2. A part of the exhaust gas in the exhaust pipe 8 flows into the intake pipe 2 through the EGR passage 7. Since the air supplied from the supercharger (not shown) is present in the intake pipe 2, this air is mixed with the exhaust gas, that is, the EGR gas in the intake pipe 2. And piston 1
When the valve rises to near the top dead center, the exhaust valve 6 closes and then the intake valve 3 opens.

When the intake valve 3 is opened, a mixed gas of air in the intake pipe 2 and exhaust gas (EGR gas) flows into the combustion chamber 40. As a result, the gas in the combustion chamber 40 becomes a gas having a low oxygen concentration in which air and exhaust gas (EGR gas) are mixed, and the combustion temperature is lowered by the combustion of the gas having such a low oxygen concentration, so that NOx (nitrogen oxide) The generation amount is suppressed.

[0005]

However, the above-described conventional EGR device for an internal combustion engine has the following problems.

(1) In order to recirculate the exhaust gas in the exhaust pipe 8 into the intake pipe 2 via the EGR passage 7, the pressure in the exhaust pipe 8 is kept higher than the intake pressure in the intake pipe 2. Need to. However, in a part of a normal diesel engine or a gasoline engine, since the turbocharger is supercharging, the intake pressure in the intake pipe 2 becomes higher than the pressure in the exhaust pipe 8 and EGR is not performed. The number of times increases, sufficient EGR is not performed, and the amount of NOx generated cannot be reduced.

(2) During combustion in the combustion chamber 40, the area where NOx is produced is a high temperature area around the flame. However, in the above-mentioned conventional technique, since the intake air (air) and the exhaust gas (EGR gas) are uniformly mixed in the intake pipe 2 in advance, the oxygen concentration in the combustion chamber 40 is uniformly reduced,
Therefore, it is necessary to recirculate the exhaust gas in excess of the amount required for actual combustion. This may cause damage to the engine parts that come into contact with the combustion gas and the exhaust gas due to the fine particles in the recirculated exhaust gas.

In view of the above problems of the prior art, the present invention has sufficient EGR to reduce NOx even in an engine in which the intake pressure is higher than the pressure on the exhaust side for a long period such as an engine with an exhaust turbocharger. Is done and EGR
An object of the present invention is to enable gas to be supplied to a high temperature portion in a combustion chamber and prevent damage to engine members due to an excessive amount of EGR.

[0009]

In order to solve the above problems, the present invention is an exhaust gas recirculation device for returning a part of exhaust gas to a combustion chamber in an internal combustion engine, wherein a seat portion is formed by fuel oil pressure. An inner valve that is opened to inject fuel from the fuel injection hole into the combustion chamber, and is fitted slidably on the outer periphery of the inner valve, and the gas passage and the combustion chamber are communicated with each other by opening the seat portion. An oil chamber into which an inner valve is introduced into the gas passage or an outer valve for ejecting the gas in the gas passage into the combustion chamber and one end of the outer valve faces to open and close the outer valve. An exhaust gas recirculation apparatus for an internal combustion engine, characterized in that a two-fluid injection valve including a valve is attached to a combustion chamber of the engine, and a gas passage of the two-fluid injection valve is connected to a volume portion having a predetermined volume. suggest.

According to the invention, when the hydraulic oil control device supplies the pressure oil into the oil chamber to open the outer valve at the extraction time in the preset exhaust stroke, the exhaust gas in the combustion chamber causes the outer valve to operate. After that, it is introduced into the volume section. Next, in the intake stroke, combustion air (intake air) is introduced into the combustion chamber. When the outer valve is opened by the hydraulic oil control device at the set exhaust gas injection timing after the intake valve is closed and the piston enters the compression stroke, the exhaust gas stored in the volume section is discharged. Is injected into.

Next, when the inner valve is opened at the set fuel injection timing, fuel is injected from the inner valve and ignited to form a flame. Since the flame and the exhaust gas injected from the outer valve are located relatively close to each other in the combustion chamber, direct contact between them causes the temperature in the vicinity of the hottest flame to drop, thereby reducing NOx emission. The generation amount is suppressed.

Therefore, by intensively injecting the exhaust gas to the highest temperature portion in the combustion chamber where the combustion flame is generated in the combustion chamber, the combustion temperature in the high temperature portion can be locally lowered. It is possible to lower the combustion temperature and suppress the generation of NOx with a smaller amount of exhaust gas as compared to the case where exhaust gas is recirculated to the intake system. This makes it possible to prevent the exhaust gas from damaging the periphery of the combustion chamber and the components of the intake system.

Further, it is easy to set the pressure in the combustion chamber during the extraction period of the exhaust gas from the outer valve to the volume portion higher than the pressure during the exhaust gas injection period by the outer valve, whereby the exhaust turbocharging engine Even in an engine with a high intake pressure, exhaust gas can be easily recirculated, and NOx can be reduced without any trouble.

Further, in the above invention, preferably, the volume section is provided with a pressurizing means for pressurizing a gas introduced into the volume section.

In the above invention, since the exhaust gas in the volume portion pressurized to the pressure set by the pressurizing means is injected from the outer valve to the flame generating portion in the combustion chamber at a predetermined timing, the exhaust gas from the outer valve is injected. When to extract
The timing of exhaust gas injection can be set more freely. As a result, the optimum positional relationship between the exhaust gas and the combustion flame is easily realized, and NOx can be reduced more effectively.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the constituent parts described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Only.

FIG. 1 is a partial sectional view showing an essential part of an exhaust gas recirculation system for an internal combustion engine according to a first embodiment of the present invention, FIG. 2 is an operation diagram of a two-fluid control valve, and FIG. Is. Figure 1
In FIG. 1, 1 is a piston, 9 is a cylinder, 41 is a cylinder head, 40 is a combustion chamber defined by the upper surface of the piston 1, the inner surface of the cylinder 9 and the lower surface of the cylinder head 41, 3 is an intake valve, and 2 is an intake valve. Intake pipe, 6 is an exhaust valve, and 8 is an exhaust pipe.

Reference numeral 100 denotes an injection valve, which is mounted in the vicinity of the center of the combustion chamber 40 of the cylinder head 41, and its tip portion faces the combustion chamber 40. Like the two-fluid injection valve in Japanese Patent Application No. 8-274117 filed by the applicant of the present invention, the injection valve 100 is configured by combining an inner valve and an outer valve to inject different fluids from the respective valves. It is a thing.

Reference numeral 11 is an injection valve main body, and 29 is the injection valve main body 1.
1. An outer valve fitted to the center of 1 so as to be reciprocally slidable, 24 is an inner valve fitted reciprocally slidably into a fitting hole 29a of the outer valve 29, 25 is an outer valve spring, and 25a is A spring receiver 26 for the outer valve spring 25 is an oil chamber formed in the injection valve body 11 so as to face the upper end surface 29b of the outer valve 29.
A cone-shaped outer valve seat portion 12 is provided at a lower end portion of the outer valve 29, and the seat portion 12 includes the outer valve spring 2
5 is pressed against the valve seat portion of the injection valve main body 11 by the elastic force of 5 to open the valve, hydraulic oil is introduced into the oil chamber 26, and the hydraulic oil pressure overcomes the elastic force of the outer valve spring 25.
Is opened apart from the valve seat.

Reference numeral 13 is an oil reservoir formed at the tip of the outer valve 29, and 14 is a plurality of fuel injection holes. The inner valve 24 has a cone-shaped inner valve seat portion 21 formed at its tip, and the seat portion 21 is pressed against the valve seat portion of the outer valve 29 by the elasticity of an inner valve spring (not shown). The oil sump 13 and the fuel injection hole 14 are shut off from each other.

Reference numeral 23 is a fuel passage provided in the injection valve main body 11, 22 is a fuel passage provided in the outer valve 29, and 43.
Is a fuel passage that is formed between the outer circumference of the inner valve 24 and the inner circumference of the outer valve 29 and communicates with the oil sump 13, and the fuel pressure-fed from a fuel injection pump (not shown) is the fuel passage 23. , 22, 43, and is supplied to the oil sump 13.

Reference numeral 10 is a gas passage formed in the injection valve body 11, 44 is a gas reservoir communicating with the gas passage 10, and the gas reservoir 44 faces the outer valve seat portion 12. 30 is a volume part having a predetermined volume.
The volume unit 30 is provided with an injection valve 1 via an exhaust gas pipe 32.
00 is connected to the gas passage 10 and is opened or closed by opening and closing the outer valve 29.

Reference numeral 45 is a hydraulic oil passage connected to the oil chamber 26. Reference numeral 28 is a hydraulic oil control device provided in the hydraulic oil passage 45, and controls the supply and discharge of hydraulic oil to and from the oil chamber 26 and the hydraulic oil pressure.

The operation of the exhaust gas recirculation system for an internal combustion engine having the above structure will be described. FIG. 2 is a cylinder pressure diagram (acupressure diagram) in the first embodiment shown in FIG. 2b, the outer valve 29 is opened during the exhaust stroke, and the exhaust gas in the combustion chamber 40 is being extracted into the volume portion 30, while the inner valve 21 is opened and fuel is injected into the combustion chamber in c. The period a is a period in which the outer valve 29 is opened and the exhaust gas in the volume portion 30 is ejected into the combustion chamber 40.

First, as shown in FIG. 2, when the outer valve 29 is opened during the exhaust gas extraction period b during the exhaust stroke, the exhaust gas in the combustion chamber 40 is discharged into the outer valve seat portion 12, the gas passage 10, the exhaust gas pipe. It flows into the volume section 30 through 32. Then, the outer valve 29 is closed at an appropriate time before the piston 1 reaches the top dead center after completing the exhaust stroke. At this time, the exhaust gas is filled in the system from the gas reservoir 44 of the outer valve seat portion 12 to the volume portion 30 via the gas passage 10 and the exhaust gas pipe 32.

When the outer valve 29 is opened,
The hydraulic oil control device 28 raises the hydraulic oil pressure in the oil chamber 26 of the injection valve 100 so that the hydraulic oil pressure overcomes the elasticity of the outer valve spring 25. After the piston 1 reaches the top dead center, when it is time to descend from the top dead center,
The intake valve 3 opens, and air is introduced into the combustion chamber 40 through the intake pipe 2. Then, the intake valve 3 closes when the piston 1 reaches the top dead center.

Next, when the hydraulic oil control device 28 increases the hydraulic oil pressure in the oil chamber 26 of the injection valve 100 at an arbitrary time after the piston 1 starts to rise from the top dead center and enters the compression stroke, This hydraulic pressure acts on the upper surface 29a of the outer valve 29 to overcome the elastic force of the outer valve spring 25 and open the outer valve 29. By opening the outer valve 29,
As described above, from the volume portion 30 to the outer valve seat portion 12
The exhaust gas that has reached the temperature is injected into the combustion chamber 40. This period is the exhaust gas injection period shown in FIG.

Next, the piston 1 reaches near the top dead center, and
When the fuel injection timing c is reached, the fuel injection pump (not shown)
The inner valve 24 is opened (the seat portion 21 is opened) by the pressure of the high-pressure fuel introduced into the oil sump 13 from the fuel passages 23, 22 and 43 from the fuel injection hole 14 to the combustion chamber 40.
A flame is generated in the combustion chamber 40 by being injected into the inside.

Here, as shown in FIG. 3, the exhaust gas 18 injected from the outer valve 29 and the flame 17 generated by the fuel injection.
Since the positional relationship of the regions where they exist in the combustion chamber 40 is relatively swathed, the temperature of the vicinity of the flame is lowered by the exhaust gas 18 coming into direct contact with the flame 17, which causes The NOx generation amount is efficiently suppressed.

Therefore, by exhausting the exhaust gas intensively to the high temperature portion in the combustion chamber 40 where the flame 17 is generated, the amount of exhaust gas can be increased as compared with the conventional means for returning the exhaust gas to the intake system. As a result, exhaust gas can prevent damage to the components of the intake system around the combustion chamber.

Further, the pressure in the combustion chamber 40 (cylinder pressure) in the exhaust gas extraction period b is set to the exhaust gas injection period a.
If the pressure is set higher than the internal pressure of the combustion chamber 40, the EGR can be extremely easily performed even in an engine equipped with an exhaust turbocharger and the intake pressure is high, and NOx can be reduced more effectively.

FIG. 4 is a configuration diagram of an exhaust gas recirculation system for an internal combustion engine according to a second embodiment of the present invention, and FIG. 5 is a cylinder pressure diagram. In this embodiment, the volume unit 30
Is provided with a compression device 27 such as a piston. That is, in FIG. 4, reference numeral 30 denotes a volume portion, which is connected to the gas passage 10 of the injection valve 100 via the exhaust gas pipe 32.
Reference numeral 27 denotes a compression device for compressing the exhaust gas in the volume section 30, which is composed of a piston or the like.

In the second embodiment, as shown in FIG. 5, the compressor 2 is opened during the compression period d before the period a when the outer valve 29 is opened and the exhaust gas is ejected into the combustion chamber 40.
7 is driven to increase the pressure by compressing the exhaust gas in the volume 30, and the compressed exhaust gas is ejected into the combustion chamber 40 when the outer valve 29 is opened.

Therefore, in the case of this embodiment, the exhaust gas 18 raised to a predetermined pressure is ejected to the flame 17 forming portion by combustion injection at a predetermined timing (FIG. 3).
Since the exhaust gas extraction period b and the exhaust gas injection period a by the outer valve 29 can be set more freely than in the first embodiment, the exhaust gas 18 and the flame 17 as shown in FIG.
It becomes easier to realize a close positional relationship with, and NOx can be reduced more efficiently.

[0035]

As described above, according to the present invention, exhaust gas is intensively injected into the highest temperature portion where combustion flame is generated in the combustion chamber, so that the combustion temperature of the high temperature portion is locally reduced. As a result, the combustion temperature can be lowered and the generation of NOx can be suppressed with a smaller amount of exhaust gas as compared with the prior art in which exhaust gas is recirculated to the intake system. This makes it possible to prevent the exhaust gas from damaging the periphery of the combustion chamber and the components of the intake system.

Furthermore, it is possible to easily set the combustion chamber pressure during the extraction period of the exhaust gas from the outer valve to the volume portion higher than the pressure during the exhaust gas injection period by the outer valve. As a result, the exhaust gas can be easily recirculated even in an engine having a high intake pressure, such as an exhaust turbocharged engine, and NOx can be reduced without any trouble.

According to the second aspect of the invention, the exhaust gas pressurized to a predetermined pressure can be injected from the outer valve to the flame producing section in the combustion chamber at a predetermined timing. The exhaust gas extraction timing and the exhaust gas injection timing can be set more freely. This makes it easier to achieve the optimum positional relationship between the exhaust gas and the combustion flame,
NOx can be reduced more effectively.

[Brief description of drawings]

FIG. 1 is a configuration diagram (a main-portion cross-sectional view) of an exhaust gas recirculation device for an internal combustion engine according to a first embodiment of the present invention.

FIG. 2 is a cylinder internal pressure diagram in the first embodiment.

FIG. 3 is an operation explanatory view of exhaust gas recirculation in the first embodiment.

FIG. 4 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 5 is a cylinder pressure diagram in the second embodiment.

FIG. 6 is a configuration diagram showing an exhaust gas recirculation device for an internal combustion engine according to a conventional technique.

[Explanation of symbols]

10 gas passages 11 Injection valve body 12 Outside valve seat 13 oil sump 14 Fuel injection holes 21 Inner valve seat 22, 23, 43 Fuel passage 24 Inside valve 25 Outer valve spring 26 oil chamber 27 Compressor 28 Hydraulic oil control device 29 Outer valve 30 volume 40 Combustion chamber 41 cylinder head 44 gas reservoir 45 hydraulic oil passage 100 injection valve

Continuation of the front page (56) Reference JP-A-9-53485 (JP, A) JP-A-8-4600 (JP, A) JP-A-6-317225 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) F02M 25/07 580 F02M 61/10 F02M 61/18 360 F02M 67/06 F02M 67/12

Claims (2)

(57) [Claims] 1. An exhaust gas recirculation device for returning a part of exhaust gas to a combustion chamber in an internal combustion engine, wherein a seat portion is opened by fuel oil pressure to inject fuel from a fuel injection hole into the combustion chamber. A valve and an outer periphery of the inner valve so as to be slidable relative to each other, and by opening a seat portion, the gas passage is communicated with the combustion chamber to introduce the gas in the combustion chamber into the gas passage, or A two-fluid injection valve having an outer valve for ejecting gas in the passage into the combustion chamber and an oil chamber into which one end of the outer valve faces and into which operating oil for opening and closing the outer valve is introduced is provided in the combustion chamber of the engine. The exhaust gas recirculation device for an internal combustion engine, wherein the gas passage of the two-fluid injection valve is connected to a volume portion having a predetermined volume. 2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the volume section is provided with a pressurizing means for pressurizing the gas introduced into the volume section.