JPH10325367A - Engine exhaust gas recirculation system - Google Patents

Abstract

(57) [Problem] To reduce the variation in exhaust gas recirculation rate between cylinders by promoting the mixing of recirculated gas and intake gas introduced into an intake pipe. SOLUTION: A recirculation gas inlet 4 into an intake pipe 1 is started at a position about 1.3 times the diameter D of the intake pipe from the axis of a throttle valve 3 in the direction of intake gas flow on the intake pipe wall surface. Then, an opening is made in an oval shape ending at a position of about 1.8 times. As a result, the reflux gas is introduced into the reverse flow region of the intake gas to promote mixing.

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 (EGR) device for an engine for improving fuel efficiency or reducing exhaust gas by recirculating exhaust gas.

[0002]

2. Description of the Related Art In recent years, during normal operation requiring no output, a part of exhaust gas is externally recirculated from an exhaust system with the aim of reducing CO ₂ or NOx emission by improving fuel efficiency due to increased interest in the environment. Various exhaust gas recirculation devices that recirculate to an intake system via a passage have been proposed.

As a conventional exhaust gas recirculation device for an engine, besides an exhaust gas recirculation device having a single circular recirculation gas inlet opening on an intake pipe wall downstream of a throttle valve of an intake system, Japanese Unexamined Utility Model Publication No. 3-114563, Heikai 3-114564
And the like disclosed in Japanese Patent Application Laid-Open Publication No. H10-260, are known. Heikai 3-
The device described in Japanese Patent Publication No. 114563 communicates with the inside of the intake pipe from the gas guide groove disposed around the intake pipe at two horizontally opposed reflux gas inlets to promote the mixing of the intake gas and the reflux gas. I do.

In the apparatus described in Japanese Utility Model Laid-Open No. 3-114564, an annular passage through which the reflux gas is introduced is formed on the outer periphery of the intake pipe, and a plurality of reflux gas inlets are formed on the wall of the intake pipe separating the annular passage and the inside of the intake pipe. To promote mixing of the intake gas and the recirculated gas. In each case, the purpose is to reduce the variation in the exhaust gas recirculation rate between the suction cylinders.

[0005]

However, in the conventional exhaust gas recirculation device described above, the recirculation gas inlet to the intake pipe is not arranged at an optimum position, and the shape of the inlet is circular. And the area is small. Therefore, when a large amount of exhaust gas recirculation is performed, the flow rate of the recirculated gas is increased, so that the inflow speed into the intake pipe is increased, and the intake gas and the recirculated gas are not sufficiently mixed. As a result, variations in the exhaust gas recirculation rate between the suction cylinders increase, leading to deterioration of engine stability, increase of emissions, and deterioration of fuel efficiency.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an exhaust gas recirculation system for an engine capable of improving the variation of the exhaust gas recirculation rate between the suction cylinders. is there.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention has been made by focusing on the physical phenomenon of intake gas during engine operation. According to the first aspect of the present invention, in the exhaust gas recirculation device for an engine that recirculates a part of the exhaust gas from the exhaust system to the intake pipe downstream of the throttle valve of the intake system via the external recirculation path, the recirculation gas inlet to the intake pipe is provided. Starts from a position about 1.3 times the diameter of the intake pipe from the throttle valve shaft center (center of the rotation axis) in the direction of intake gas flow on the intake pipe wall surface, and ends at a position about 1.8 times the diameter of the intake pipe. The opening is formed in an oval shape.

That is, a reverse flow region of the intake gas is generated downstream of the throttle valve, and the expansion of the reverse flow region increases or decreases depending on engine operating conditions. The tip of the stably formed backflow region is about 1.3 to 1.8 times the intake pipe diameter from the throttle valve shaft center. Therefore, utilizing the intake gas backflow phenomenon under the operation of the engine, the recirculation gas introduction port into the intake pipe is provided on the wall of the intake pipe in the direction of the intake gas in the direction of the intake gas by about 1. 3
The opening was made in an oval shape starting from the doubled position and ending at the approximately 1.8-fold position.

Thus, an opening area capable of coping with an increase in the flow rate of the reflux gas is secured, and the reflux gas is stably introduced into the reverse flow region. And the variation in the exhaust gas recirculation rate between the suction cylinders can be reduced even under a large amount of exhaust gas recirculation rate. In the invention according to claim 2, the recirculation gas introduction port is formed in a circular shape on an intake pipe wall separating the annular recirculation gas guide space formed on the outer circumference of the intake pipe so as to communicate with the external recirculation path and the inside of the intake pipe. It is characterized in that a plurality are arranged side by side in the circumferential direction.

[0010] In the invention according to claim 3, the plurality of recirculation gas inlets are located from a base point in a circumferential direction of an intake pipe wall surface with respect to a pipe position of an external recirculation passage provided in the annular recirculation gas guide space. It is characterized in that the aperture area increases as the distance increases. The invention according to claim 4 is characterized in that a gas-permeable member is arranged at each of the plurality of reflux gas inlets, and the ventilation resistance is changed depending on the circumferential position of each of the reflux gas inlets. .

[0011]

According to the first aspect of the present invention, an opening area capable of coping with an increase in the flow rate of the recirculated gas is secured, and
Since the exhaust gas can be introduced into the reverse flow area in which the flow circulates, the mixing of the intake gas and the recirculation gas is promoted, the variation in the exhaust gas recirculation rate between cylinders can be reduced, and the effects of improving fuel efficiency and exhaust can be obtained.

According to the second aspect of the present invention, since the plurality of recirculation gas inlets are introduced into the reverse flow region from almost the entire circumferential direction, the mixing of the intake gas and the recirculation gas is further promoted, and the exhaust gas recirculation rate is reduced. Variation can be further reduced. Further, even under a large amount of exhaust gas recirculation rate, the position and area of the recirculation gas inlet can be arranged according to the recirculation amount. According to the third aspect of the present invention, the area of the reflux gas inlet is increased in the circumferential direction with the piping position of the external reflux passage as a base point, and a plurality of irregularly shaped reflux gas inlets are provided. , The gas is uniformly introduced into the backflow region, so that the bias of the recirculation gas in the backflow region is eliminated, the mixing of the intake gas and the recirculation gas is further promoted, and the variation in the exhaust gas recirculation rate can be further reduced.

According to the fourth aspect of the present invention, by changing the ventilation resistance of the plurality of reflux gas inlets depending on the circumferential position, the reflux gas introduction flow rate corresponding to the flow rate distribution of the main flow in the intake pipe is reduced. Since the reflux gas is controlled and more uniformly introduced into the backflow region, the mixing of the intake gas and the reflux gas is further promoted, and the variation in the exhaust gas recirculation rate can be further reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. A throttle body 2 is connected upstream of an intake pipe 1 having a branch pipe and a collector, and a throttle valve 3 is provided in the throttle body 2.

A recirculation gas inlet 4 is provided on a wall surface of the intake pipe 1 downstream of the throttle valve 3. The recirculation gas inlet 4 has an oval shape that is long in the flow direction of the intake gas, and its opening surface in the flow direction starts at a position 1.3 times the diameter of the intake pipe from the axis of the throttle valve 3 and is 1.8. End at double position. In other words, assuming that the diameter of the intake pipe is D, the operation starts from a position 1.3D from the axis of the throttle valve 3.
End at position 8D.

A recirculation gas pipe 5 as an external recirculation path for guiding a part of exhaust gas from the engine exhaust system is connected to one end of a connection pipe 7 by a flare nut 6. The connecting pipe 7 changes its cross-sectional shape from one end to the other end, forms an oval with the same shape as the reflux gas inlet 4 on the other end side, and connects to the intake pipe 1 via the gasket 8 on the mounting flange surface. It is fixed with bolts.

Next, the operation will be described. FIG. 2 shows the flow downstream of the throttle valve in the intake pipe. On the back of the throttle valve, there is a reverse flow area in which the flow circulates with respect to the main flow. FIG. 3 shows a normal operation region represented by the engine speed and the throttle opening. In this normal operation area, EGR
Is a region excluding a high load close to WTO and a low load near idle.

FIG. 4 shows the size of the reverse flow area with respect to the throttle opening. The size of the backflow area depends on the throttle opening. Therefore, the EG having a high load in the EGR region of FIG.
Attention is paid to the state of the reverse flow region under the R region high load condition and the EGR region low load condition with a low load. FIG. 5 shows a reverse flow region under the EGR region low load condition and the EGR region high load condition. As shown in FIG. 3, the size of the reverse flow area depends on the throttle opening. Therefore, under the low load condition, the backflow area becomes large, and the backflow stable position where the backflow occurs stably is about 1.8 times the intake pipe diameter D. In a high load condition, the backflow stable position is about 1.3 times the intake pipe diameter D.

FIG. 6 shows the influence of the reflux gas introduction position. When the reflux gas is introduced from downstream of the backflow region (1), since the reflux gas is flowed downstream as it is, mixing of the fresh air with the intake gas does not proceed and the mixing state is poor. In addition, when the recirculation gas is introduced from the vicinity of the throttle valve considerably upstream of the backflow stable position (3), the recirculation gas directly hits the throttle valve without being mixed with the intake air. Therefore, a deposit is formed in the throttle valve. Immediately after hitting the throttle valve, the air flows in the mainstream and goes out of the reverse flow area and flows downstream, so that mixing with the intake air does not progress much. On the other hand, when the reflux gas is introduced within a range of 1.3 to 1.8 times the diameter D of the intake pipe near the stable backflow position (2), the reflux gas stays in the backflow region for a long time. Mixing with the intake air proceeds, and the mixing state improves. The conventional reflux gas introduction position is located considerably downstream of the throttle valve, and the reflux gas is introduced from the downstream side of the reverse flow area (see Japanese Patent Application Laid-Open No. 8-218949).

FIG. 7 shows the effect of this embodiment, and FIG. 8 shows the relationship between the position of the reflux gas inlet and the backflow region in this embodiment. In the present embodiment, by making extensive use of the region of the backflow stable position, mixing with the intake air is promoted even at a large exhaust gas recirculation rate and under pulsating conditions during engine operation, and the exhaust gas recirculation rate between cylinders is increased. Variation can be reduced. Next, a second embodiment shown in FIGS. 9 and 10 will be described.

In this embodiment, a part of the intake pipe 1 is enlarged,
A partition liner 9 is inserted and press-fitted into this portion to form an intake pipe wall surface, and an annular reflux gas guide space 10 is formed outside the wall. Above or below the outer wall of the reflux gas guide space 10, a reflux gas pipe 5 is connected and fixed by a flare nut 6. Then, on the partition liner 9, except for a position facing the connection position of the reflux gas pipe 5, the first liner is arranged in the circumferential direction, and
A plurality of oblong reflux gas inlets 4 are formed in the same manner as in the embodiment.

As a result, the recirculated gas flowing from the recirculated gas pipe 5 into the recirculated gas guide space 10 collides with the partition liner 9 and is diverted right and left.
The air is further introduced into the reverse flow area in the intake pipe 1. Since the gas is introduced into the backflow region from the entire circumference in this way, the mixing of the intake gas and the recirculation gas in the backflow region is promoted, and the variation in the exhaust gas recirculation rate can be reduced. Further, even under a large amount of exhaust gas recirculation rate, the position and area of the recirculation gas inlet can be arranged according to the recirculation amount.

Next, a third embodiment shown in FIG. 11 will be described. In this embodiment, since the recirculation gas is most likely to enter the intake pipe 1 from the recirculation gas inlet 4 near the position of the recirculation gas pipe 5, the area of the recirculation gas introduction port 4 is set to the left and right with the position of the recirculation gas pipe 5 as a base point. By increasing the diameter in the circumferential direction, the gas can be uniformly introduced into the reverse flow area in the intake pipe 1 from the entire circumference.

Accordingly, there is no bias in the recirculation gas in the backflow region, the mixing of the intake gas and the recirculation gas is promoted, and the variation in the exhaust gas recirculation rate can be reduced. Next, a fourth embodiment shown in FIGS. 12 and 13 will be described. In this embodiment, after the partition liner 9 is inserted and press-fitted, a plurality of recirculated gas is introduced by lightly press-fitting a mesh-shaped filter 11 which is a gas permeable member to the outside (to the reflux gas guide space 10). The mouth 4 is covered with a filter 11.

Then, the ventilation resistance of the filter 11 is changed at the circumferential position of the reflux gas inlet 4. Specifically, as shown in FIG. 14, in the vertical position where the main flow velocity is large in the intake pipe 1 (see FIG. 2), the ventilation resistance is reduced, and the horizontal position where the main flow velocity is small and the distance from the wall surface to the reverse flow area is short. Then, increase the ventilation resistance. By controlling the inflow velocity of the recirculation gas in this way and promoting uniform introduction to the backflow region in the intake pipe 1 from the entire circumference, the bias of the recirculation gas in the backflow region can be further improved even under a large amount of exhaust gas recirculation rate. And the variation in the exhaust gas recirculation rate can be further reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a flow downstream of a throttle valve.

FIG. 3 is a diagram for explaining an EGR region during operating conditions;

FIG. 4 is a diagram showing the relationship between the throttle opening and the size of a reverse flow area.

FIG. 5 is a diagram illustrating a change in a backflow area due to a load condition;

FIG. 6 is a view for explaining the flow of the reflux gas when the reflux gas introduction position is changed.

FIG. 7 is a diagram showing the effect of the first embodiment.

FIG. 8 is a diagram showing the relationship between the position of the reflux gas inlet and the backflow area.

FIG. 9 is a configuration diagram of a second embodiment of the present invention.

FIG. 10 is a perspective view of the second embodiment.

FIG. 11 is a perspective view of a third embodiment of the present invention.

FIG. 12 is a configuration diagram of a third embodiment of the present invention.

FIG. 13 is a perspective view of the fourth embodiment.

FIG. 14 is a characteristic diagram of the permeable member according to the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intake pipe 2 Throttle body 3 Throttle valve 4 Reflux gas inlet 5 Reflux gas piping 6 Flare nut 7 Connection pipe 8 Gasket 9 Partition liner 10 Reflux gas guide space 11 Filter (air-permeable member)

Claims (4)

[Claims] An exhaust gas recirculation device for an engine for recirculating a part of exhaust gas from an exhaust system to an intake pipe downstream of a throttle valve of an intake system via an external recirculation passage. On the pipe wall, an opening is formed in an oval shape that starts at a position approximately 1.3 times the diameter of the intake pipe from the axis of the throttle valve and ends at a position about 1.8 times the diameter of the throttle valve in the direction of intake gas flow An exhaust gas recirculation device for an engine. 2. The recirculation gas introduction port is provided on an intake pipe wall separating an annular recirculation gas guide space formed on the outer periphery of the intake pipe so as to communicate with an external recirculation path and the inside of the intake pipe. 2. The exhaust gas recirculation device for an engine according to claim 1, wherein a plurality of the exhaust gas recirculation devices are arranged side by side. 3. The plurality of recirculation gas introduction ports are located farther from the base point in the circumferential direction of the wall surface of the intake pipe with respect to the pipe position of the external recirculation passage provided in the annular reflux gas guide space. 3. The exhaust gas recirculation device for an engine according to claim 2, wherein the opening area is increased. 4. A gas permeable member is disposed at each of the plurality of reflux gas inlets, and the air flow resistance is changed depending on the circumferential position of each of the reflux gas inlets. Or an exhaust gas recirculation device for an engine according to claim 2.