JP2000249004A - Egr device provided with reed valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a pressure difference between exhaust pressure and boost pressure so as to carry out sufficient EGR by disposing a pressure difference increasing means such as a throttle valve and a venturi part in an intake passage, in an internal combustion engine such as a diesel engine with a turbo supercharger. SOLUTION: In an EGR device 1 wherein an exhaust passage and intake passages 3 in an engine E with a supercharger are connected to each other through EGR passages 4A and reed valves 8 are disposed to allow flow from the EGR passage 4A toward the intake passages 3 and to obstruct flow of a reverse direction, pressure difference increasing means 6 are disposed to increase a pressure difference Pe-Pb between exhaust pressure Pe including pulsation and boost pressure Pb.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR device having a reed valve for a turbocharged diesel engine or the like.

[0002]

2. Description of the Related Art In measures against exhaust gas from engines such as diesel engines, in order to reduce the amount of NOx emitted from exhaust gas, a part of the exhaust gas, which is an inert gas, is recirculated to intake air to reduce the combustion temperature. It is known that EGR (exhaust gas recirculation), which suppresses NOx generation by keeping it low, is effective
It is widely used.

[0003] In an EGR device 10 provided in the supercharged engine E, as shown in FIG.
The EGR passage 14 connects the exhaust manifold 2a, which is the exhaust manifold, and the intake pipe 3b, which is the intake passage 3, to the EGR passage 14.
By providing a GR valve 15 and an EGR cooler 14c, the EGR gas G
The exhaust gas is recirculated by adjusting the flow rate of e and cooling.

The flow rate of the EGR gas Ge is obtained by inputting the engine speed Ne and the engine load Lo from a sensor group (not shown), and calculating the EG from the operating state corresponding to the input values.
The EGR valve 15 is adjusted and controlled by a controller 16 called an engine control unit (ECU) that calculates whether or not to perform R and a target EGR amount Qge and outputs a signal for distributing the target EGR amount Qge. Is being done.

[0005] In order to improve the effect of reducing NOx in the exhaust gas Go, it is necessary to perform EGR even in a high load region where the amount of NOx emission is large.
, The turbine 7a of the supercharger 7 provided at the outlet of the exhaust manifold 2a is driven by the exhaust gas Go, and the compressor 7b on the side of the intake pipe 3b driven by the turbine 7a compresses the intake air Ai to increase the boost pressure. (Intake pressure) Pb is increased.

Therefore, in the operating region A of the engine shown by oblique lines in FIG. 7, that is, in the operating region A of the engine in which the engine speed Ne is low speed and medium speed, and the engine load is medium load and high load, FIG. As described above, since the average pressure Pbm of the boost pressure Pb becomes higher than the average pressure Pem of the exhaust pressure Pe, a part of the exhaust gas G is used as the EGR gas Ge.
It becomes difficult to recirculate to the intake side.

The engine operating range A in which the EGR is difficult
In order to perform as much EGR as possible, the pulsation phenomenon of the intake pressure Pb and the exhaust pressure Pe is used.
As shown in FIG. 13, a reed valve 8 is provided in the EGR passage 14.

Even if the average pressure is boost pressure Pbm> exhaust pressure Pem, the reed valve 8 instantaneously generates a hatched portion Z where the boost pressure Pb <exhaust pressure Pe due to exhaust pulsation. By opening the reed valve 8 at the portion Z, the EGR gas Ge can flow into the intake manifold 3a, and EGR can be performed to reduce NOx.

Also, boost pressure Pb other than this part Z>
At the exhaust pressure Pe, the reed valve 8 closes, so that backflow of the intake air Ai from the supply side to the exhaust side is prevented, deterioration of engine combustion is prevented, and deterioration of engine performance is prevented. it can.

That is, in a turbocharged diesel engine or the like, the average pressure Pbm in the intake manifold 3a, which is the intake passage 3, is higher than the average pressure Pem in the exhaust manifold 2a, which is the exhaust passage 2. Although it may be difficult to perform this operation, by arranging a one-way valve (return valve) such as the reed valve 8 in the EGR passage 14,
The pressure difference (Pe) generated by the pulsation in each passage 2a, 3a
-Pb) is used to perform EGR.

[0011]

However, even in the EGR device 10 provided with the reed valve 8, when the combustion temperature becomes high during a high load operation or the like and a large amount of EGR is desired to be performed, the boost pressure Pb is reduced. Rise, exhaust pressure P
pressure difference due to pulsation between e and the boost pressure Pb (Pe-P
There is a problem that a sufficient amount of EGR gas cannot be supplied because b) is insufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. It is an object of the present invention to provide an internal combustion engine, such as a diesel engine with a turbocharger, having a throttle portion, a venturi portion, and the like in an intake passage. To provide an EGR device having a reed valve capable of performing sufficient EGR by increasing the pressure difference (Pe−Pb) between the exhaust pressure Pe and the boost pressure Pb by providing the pressure difference expanding means. It is in.

[0013]

An EGR device provided with a reed valve for achieving the above object is configured as follows. 1) The exhaust passage and the intake passage of the supercharged engine are EG
In an EGR device which is connected by an R passage and which is provided with a reed valve for allowing a flow in the direction of the intake passage to the EGR passage and preventing a flow in the reverse direction, a pressure between an exhaust pressure including a pulsation and a boost pressure is provided. It is provided with pressure difference expanding means for expanding the difference. 2) The pressure difference expanding means is constituted by a throttle provided in the EGR passage, and the reed valve is provided in the throttle. 3) Alternatively, the pressure difference increasing means is constituted by a venturi portion provided at a junction opening of the EGR passage to the intake passage. 4) Further, the pressure difference expanding means is constituted by a venturi portion provided at a joining opening of the EGR passage to the intake passage, and further, the reed valve is provided at the joining opening.

According to the above configuration, the pressure difference (Pe) between the exhaust pressure Pe and the boost pressure Pb is increased by the pressure difference expanding means such as the throttle portion of the EGR passage and the venturi portion of the intake passage.
Since −Pb) is enlarged, a large amount of EGR gas can be circulated, and EGR can be performed efficiently to reduce NOx.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] E equipped with a reed valve according to the present invention
In the first embodiment of the GR device, as shown in FIGS. 1 and 2, an exhaust manifold 2a as an exhaust passage 2 and an intake pipe 3b as an intake passage 3 of an engine E with a supercharger are connected to an EG.
The EGR passage 4A is connected by an R passage 4A, and a throttle portion 6 is provided in the EGR passage 4A. The throttle portion 6 is provided with a reed valve 8 for allowing a flow in the direction toward the intake passage 3 and preventing a flow in the reverse direction. I do.

An EGR valve 5 for adjusting the EGR amount and an EGR cooler 4c for cooling the EGR gas Ge are provided in the EGR passage 4A, and a compressor 7b of the supercharger 7 is provided in the intake pipe 3b. And compressed intake Ai
Is provided with an intercooler 3c for cooling the water.
The compressor 7b is connected to and driven by a turbine 7a driven by the exhaust gas Go.

The structure of the reed valve 8 is as shown in FIG.
The EGR gas Ge is formed by attaching a bolt 82 through a bolt hole 84a so that the stopper 82 is on the outside.
In one direction only.

EGR device 1 having a reed valve of this configuration
According to this, the throttle section 6 is provided in the EGR pipe 4Aa, and the cross-sectional area is reduced by reducing the diameter of the pipe to which the reed valve 8 is attached and the pipe diameter immediately before the reed valve 8, so that the upstream side of the reed valve 8 as shown in FIG. The amplitude of the pulsation of the exhaust pressure Pe is set to be smaller than that in the case where there is no throttle as shown in FIG.
Pulsation amplitude can be enlarged.

Accordingly, the exhaust pressure Pe on the upstream side of the throttle 6
Since the pressure difference (Pe2−Pb) between the pressure E2 and the boost pressure Pb can be increased, the flow rate of the passing EGR gas Ge can be increased, and EGR can be performed with a sufficient amount of EGR gas to reduce NOx.

[Second Embodiment] Next, a second embodiment of the EGR device provided with the reed valve according to the present invention will be described. In this second embodiment, FIGS.
As shown in (2), a venturi section 9 is provided at a merging opening 4d at a portion where the EGR passage 4 merges with the intake passage 3A as a pressure difference increasing means of the supercharged engine E.

The throat of the venturi section 9 reduces the cross-sectional area of the intake passage 3A to increase the flow velocity, thereby increasing the dynamic pressure and reducing the static pressure. That is, at the throat of the venturi section 9, the static pressure Pb of the intake passage 3A is reduced, so that the EGR gas is easily sucked. And E
The GR passage 4 is provided with a reed valve 8A that allows a flow in the direction toward the intake passage 3A and prevents a flow in the reverse direction.

EGR device 1 having a reed valve of this configuration
According to A, due to the venturi section 9 of the intake passage 3A,
The intake pressure (boost pressure) Pb can be reduced as a whole and the average value Pbm can be reduced, and the intake pressure (boost pressure) Pb as shown in FIG. 8 is reduced to the boost pressure Pb2 as shown in FIG. can do.

Therefore, the boost pressure Pb2 and the exhaust pressure Pe
Is larger than the pressure difference (Pe-Pb) upstream of the venturi section 9, a large amount of EGR gas can be circulated, and sufficient EGR can be performed.

[Third Embodiment] Next, a third embodiment of the EGR device provided with a reed valve according to the present invention will be described. In the third embodiment, FIGS.
As shown in FIG. 5, the confluence opening 4d of the EGR passage 4 to the intake passage 3B as a pressure difference increasing means of the supercharged engine E.
The venturi section 9 is provided in the
An EGR device 1B is configured by providing a reed valve 8B for allowing flow in the direction toward the intake passage 3B and preventing flow in the reverse direction at d.

EGR device 1 having a reed valve of this configuration
According to B, similarly to the second embodiment of FIGS. 3 and 4, the pressure (boost pressure) Pb as shown in FIG. 8 is entirely reduced in the venturi section 9 of the intake passage 3B. 1
The boost pressure Pb2 as shown in FIG.

Therefore, the boost pressure Pb2 and the exhaust pressure Pe
Is larger than the pressure difference (Pe-Pb) upstream of the venturi section 9, a large amount of EGR gas can be circulated, and sufficient EGR can be performed. [Summary] According to the EGR devices 1, 1A, and 1B having the above-described reed valves, as in the case of high-load operation,
Even when the combustion temperature is likely to be high and a large amount of EGR gas Ge is required, a large amount of EGR gas Ge can be supplied to the intake passages 3, 3A, 3B and EGR can be performed, so that NOx can be efficiently reduced. Can be reduced.

[0027]

As described above, according to the EGR device having the reed valve of the present invention, the boost pressure (intake pressure) is increased by the pressure difference increasing means such as the throttle portion of the EGR passage and the venturi portion of the intake passage. Since the pressure difference (Pb-Pe) between Pb and the exhaust pressure Pe can be increased, the EGR
The passage amount of the EGR gas in the passage can be increased, and the EGR can be efficiently performed with a sufficient EGR gas amount and
Ox can be reduced.

In particular, in a high load state, the boost pressure increases, the fuel temperature increases, and the amount of EGR gas is desired to be increased. Therefore, the effect of the provision of the pressure difference increasing means increases.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a supercharged engine showing an EGR device including a reed valve according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged view showing a portion X in FIG. 1;

FIG. 3 is a configuration diagram of a supercharged engine showing an EGR device provided with a reed valve according to a second embodiment of the present invention.

FIG. 4 is a partially enlarged view showing a portion X in FIG. 3;

FIG. 5 is a configuration diagram of a supercharged engine showing an EGR device including a reed valve according to a third embodiment of the present invention.

FIG. 6 is a partially enlarged view showing a portion X in FIG. 5;

FIG. 7 is a diagram illustrating the relationship between boost pressure and exhaust pressure with respect to engine torque and engine speed for explaining the operation of a reed valve.

FIG. 8 is a diagram illustrating a pulsating state of a boost pressure and an exhaust pressure with respect to a crank angle for explaining an operation of a reed valve.

FIG. 9 is a diagram illustrating a pulsating state of the boost pressure and the exhaust pressure with respect to the crank angle for illustrating the effect of the pressure difference expanding means in the first embodiment.

FIG. 10 is a diagram illustrating a pulsating state of a boost pressure and an exhaust pressure with respect to a crank angle for illustrating an effect of a pressure difference expanding unit in the second and third embodiments.

11A and 11B are diagrams illustrating a configuration example of a reed valve according to the present invention, wherein FIG. 11A is a side sectional view of the reed valve, FIG. 11B is a plan view of a reed, and FIG. 11C is a plan view of a stopper. (D) is a perspective view of the case, and (e) is a perspective view of the reed valve.

FIG. 12 is a configuration diagram of a supercharged engine showing an EGR device having a prior art reed valve.

FIG. 13 is a partially enlarged view showing a portion X in FIG. 12;

[Explanation of symbols]

 1, 1A, 1B EGR device provided with reed valve 2 Exhaust passage 3, 3A, 3B Intake passage 4 EGR passage 4d Merging opening 6 Restrictor (pressure difference expanding means) 8, 8A, 8B Reed valve (check valve) 9 Venturi part (pressure difference expanding means) E Engine with turbocharger Pb Boost pressure Pe Exhaust pressure

Claims (4)

[Claims] An exhaust passage and an intake passage of a supercharged engine are connected by an EGR passage, and a reed valve for allowing a flow in the EGR passage in a direction toward the intake passage and preventing a flow in a reverse direction is provided. An EGR device provided with a reed valve, characterized in that the EGR device provided includes a pressure difference expanding means for expanding a pressure difference between exhaust pressure including pulsation and boost pressure. 2. The E according to claim 1, wherein said pressure difference increasing means is a throttle provided in said EGR passage, and said reed valve is provided in said throttle.
GR device. 3. The EGR device according to claim 1, wherein said pressure difference increasing means is a venturi portion provided at a junction of said EGR passage with said intake passage. 4. The pressure difference increasing means is a venturi portion provided at a junction opening of the EGR passage to the intake passage, and the reed valve is provided at the junction opening. An EGR device comprising the reed valve according to claim 1.