JP3444175B2 - Engine exhaust gas recirculation system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas recirculation device (EGR device) for improving fuel efficiency or exhaust performance by recirculating exhaust gas.

[0002]

2. Description of the Related Art In recent years, due to growing concern about the environment,
During normal operation where high output is not required, CO ₂ emissions are reduced by improving fuel efficiency or NOx is reduced by lowering combustion temperature.
Various exhaust gas recirculation devices (EGR devices) that return part of exhaust gas to the intake system have been proposed in order to reduce the amount of exhaust gas.

As a conventional exhaust gas recirculation device, for example, an example shown in FIG. 13 (Japanese Utility Model Laid-Open No. 3-114563), an example shown in FIG. 14 (Japanese Utility Model Laid-Open No. 3-114564), and an example shown in FIG. No. 218949) is known.

In FIG. 13, the EGR gas from the gas introduction passage 1 is introduced through the gas guide groove 3 provided around the intake pipe 2 through the two openings 4 which are horizontally opposed to each other.
Introduced into the inside, fresh air and EGR gas are mixed. In addition, in the case of FIG. 14, an annular passage 6 into which EGR gas is introduced is formed on the outer circumference of the intake pipe 5 and is introduced into the intake pipe 5, whereby fresh air and EGR gas are mixed. They are,
All of them are intended to reduce variations in the EGR rate between the cylinders.

Further, in FIG. 15, a second surge tank 12 is provided in the intake passage 10 downstream of the first surge tank 11, and the EGR gas introducing section 1 is provided in the second surge tank.
3 is arranged. By thus introducing the EGR gas at a position distant from the throttle valve 14, it is possible to prevent the deteriorated portion (deposit) of the exhaust gas from adhering to the throttle valve 14.

[0006]

[Problems to be solved by the invention] However,
In the conventional exhaust gas recirculation device, EGR to the intake pipe
It cannot be said that the gas introduction part is in the optimum position and direction.

For example, as shown in FIG. 13, only EGR gas is introduced from the openings 4 facing each other in the horizontal direction, or
As shown in FIG. 14, it was not possible to satisfactorily mix the EGR gas and the fresh air only by introducing the EGR gas from the hole 7 provided in the wall surface of the intake pipe 5. Further, in the case of FIG. 14, the mixing of the EGR gas and the fresh air becomes insufficient, or the EGR gas is in the reverse flow area depending on the operating conditions, that is, the state of the fresh air flow and the reverse flow area when the opening of the throttle valve changes. Gas entered and deposits increased. Further, as shown in FIG. 15, in the case where EGR gas is introduced into the second surge tank 12, it is difficult to evenly distribute the EGR gas from the surge tank 12 to each cylinder.

Therefore, when a large amount of EGR is carried out, the mixing of the EGR gas and the fresh air becomes insufficient, and as a result, the EGR rate among the cylinders varies, which deteriorates the stability of the engine and reduces emissions. It was a cause of increase and deterioration of fuel efficiency. Further, there is a concern that the throttle valve may become stuck due to the formation of deposits on the throttle valve, or the accuracy of controlling the intake air amount may deteriorate.

The present invention has been made in view of such a conventional problem, and provides an EGR device for an engine which improves the variation in EGR rate among cylinders and prevents the formation of deposits on a throttle valve. It is in.

[0010]

A first aspect of the present invention has an intake system having a throttle valve interposed upstream of an intake pipe provided with a branch pipe and a collector connected to each cylinder, and an exhaust system to an external return passage. In an exhaust gas recirculation system for an engine that introduces EGR gas into an intake pipe at the rear of the throttle valve of the intake system and upstream of the collector via an EGR gas, a pair of EGR gas introduction ports from the external recirculation passage to the intake pipe are provided on both sides of the throttle valve. Arranged behind the free end and from the tangential direction of the circumference of the intake pipe cross section, opened so that the inflow direction is a cross flow opposite to each other, and at a predetermined angle downstream from the direction orthogonal to the fresh air flow of the intake pipe. It is characterized in that at least one of a distance from the throttle valve of the two EGR gas introduction ports and a downstream angle is set to different values. Than it is.

According to a second aspect of the present invention, in the first aspect of the present invention, the EGR gas introduction port provided at the rear of the forward leaning free end of the throttle valve is placed at the rear of the backward leaning free end. It is characterized in that the distance from the throttle valve of the EGR gas inlet is made shorter.

According to a third aspect of the present invention, in the first or second aspect of the invention, the downstream angle of the EGR gas inlet disposed behind the forward tilted free end of the throttle valve is disposed behind the rear tilted free end. The angle is smaller than the downstream angle of the EGR gas inlet.

According to a fourth aspect of the present invention, in the first to third aspects, when the intake pipe including the throttle body has a bend along the surface including the throttle valve axis with respect to the collector, the front of the throttle valve is provided. The EGR gas introduction port provided at the rear of the tilt free end is provided outside the bend, and the EGR gas introduction port provided at the rear of the rear tilt free end is provided at the inside of the bend. To do.

In a fifth aspect based on the first to fourth aspects, when the intake pipe including the throttle body has a bend with respect to the collector along a plane orthogonal to the throttle valve axis, the inside of the bend is The throttle valve is arranged so that the free end of the throttle valve in FIG.

[0015]

According to the first aspect of the invention, a spiral flow (spiral flow) is formed in the downstream direction of the inner circumference of the intake pipe, so that the EG
The mixing of R gas and fresh air is promoted. As a result, it is possible to reduce variations in the EGR rate among the cylinders even under a large amount of EGR rate, and it is possible to improve fuel efficiency and exhaust performance. Further, since the EGR gas is introduced from the tangential direction of the circumference, the EGR gas does not directly enter the backflow region that occurs downstream of the back surface of the throttle valve, and the deposit formation on the throttle valve can be prevented. Further, since the position and angle of the EGR gas inlet are set to the optimum ones according to the state of the fresh air main flow, the state of the reverse flow region, etc., it is possible to further reduce the variation in the EGR rate and prevent deposit formation. .

According to the second aspect of the invention, the E at the rear of the forward tilting free end is
Since the GR gas inlet is moved upstream, the distance from the EGR inlet to the most upstream side branch pipe is extended and E
The mixing time of the GR gas becomes long, the mixing of the EGR gas and the fresh air is promoted, and the variation in the EGR rate can be sufficiently reduced. Further, since the backflow region that occurs downstream of the rear surface of the throttle valve becomes smaller behind the forward tilt free end, EGR gas does not enter the backflow region, and deposit formation on the throttle valve can be prevented.

According to the third invention, E at the rear of the forward tilted free end is
Since the downstream angle of the GR gas inlet is made smaller, the pitch of the spiral flow becomes smaller, the length of the spiral flow becomes longer, and the mixing time of fresh air and EGR gas becomes longer.

As a result, the mixing of the EGR gas and the fresh air is promoted, and the variation in the EGR rate among the cylinders can be sufficiently reduced. Further, since the backflow region that occurs downstream of the back surface of the throttle valve becomes smaller behind the forward tilt free end, EGR gas does not enter the backflow region, and it is possible to prevent deposit formation on the throttle valve.

According to the fourth aspect of the invention, the E at the rear of the forward tilt free end is
Although the GR gas inlet is arranged outside the bend, if the throttle body and the collector have bends along the surface including the throttle valve axis, the backflow region that occurs downstream of the back of the throttle valve does not bend. Since it becomes smaller on the outer side, the EGR gas introduction port at the rear of the forward tilted free end can be moved upstream without causing the EGR gas to flow into the reverse flow region.

As a result, the spiral flow is extended and the mixing time between the fresh air and the EGR gas becomes long, so that the EG
Mixing of R gas and fresh air is promoted, and even with a large amount of EGR rate, variations in EGR rate among the cylinders can be sufficiently reduced. In addition, EGR is provided in the reverse flow area downstream of the throttle valve rear surface.
Since gas does not enter, deposit formation on the throttle valve can also be prevented.

According to the fifth aspect of the invention, the throttle valve is arranged so that the free end inside the bend becomes the forward tilted free end, but the throttle body and the collector are arranged along a plane orthogonal to the axis of the throttle valve. If there is a bend, the backflow region that occurs downstream of the back surface of the throttle valve becomes smaller inside the bend, so the EGR gas introduction port behind the forward tilted free end moves upstream without EGR gas flowing into the backflow region. be able to.

As a result, the spiral flow is extended and the mixing time of the EGR gas with the fresh air becomes long,
The mixing of the EGR gas and the fresh air is promoted, and the variation in the EGR rate among the cylinders can be sufficiently reduced even when the EGR rate is large. In addition, EG is provided in the reverse flow area downstream of the throttle valve rear surface.
Since R gas does not enter, formation of deposit on the throttle valve can be prevented.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show a first embodiment of the present invention, in which 20 is an engine, 21 is an intake manifold,
22 is an exhaust manifold.

The intake manifold 21 includes an intake pipe 23,
A throttle valve 27 is provided in a throttle body 26 connected to an upstream side of the intake pipe 23, which is composed of a collector 24 having a predetermined volume following the intake pipe 23 and a branch pipe 25 connected from the collector 24 to each cylinder of the engine 20. To be dressed.

The exhaust manifold 22 comprises a branch pipe 28 connected to each cylinder of the engine 20, and an exhaust pipe 30 in which the branch pipes 28 are assembled.

An EGR passage 31 (external return passage) for returning a part of the exhaust gas of the engine 20 to the intake system is branched from the exhaust pipe 30, and the EGR passage 31 has two passages 32 from the middle. It is branched into 33 and connected to the intake pipe 23 behind the throttle valve 27 of the intake system and upstream of the collector 24.

EGR gas inlet 34 of one passage 32
Is opened rearward of the rearward tilted free end 27a of the throttle valve 27, and the EGR gas inlet 35 of the other passage portion 33 is opened rearward of the forward tilted free end 27b of the throttle valve 27.

Under such a structure, the present invention uses EG
The R gas inlets 34 and 35 are respectively arranged at positions separated by 180 ° on the circumference of the cross section of the intake pipe 23 and from the tangential direction of the circumference, and are opened so that the inflow directions are opposite cross-flows. 23 is inclined in the downstream direction by a predetermined angle (lead angle) with respect to the direction perpendicular to the fresh air flow.

Further, in order to improve the effect of improving the EGR performance by the spiral flow, the throttle valve 2 of the EGR gas introduction port 35 arranged on the forward tilt free end 27b side.
The distance Lb from 7 is set shorter than the distance La from the throttle valve 27 of the EGR gas introduction port 34 disposed on the side of the rearward tilted free end 27a. The EGR gas inlet 3
4, 35 may be formed from opposite directions.

Next, the operation will be described.

4 and 5 show the flow of fresh air and EGR gas downstream of the throttle valve 27. The EGR gas introduced through the EGR gas inlets 34 and 35 is located on both free ends 27a and 27b of the throttle valve 27. Main air (upper main flow, lower main flow) of each fresh air that has passed through the intake pipe 23
Is mixed by the spiral flow in the downstream direction of the inner circumference of the.

At the downstream side of the back surface of the throttle valve 27, there is a backflow region in which fresh air circulates as shown in FIG.
If the distance L between the throttle valve 27 and the EGR gas inlet is short, the EGR gas flows into the reverse flow region. In this case, the mixing with fresh air is promoted and the variation in the EGR rate among the cylinders is reduced, but on the other hand, the EGR gas hits the throttle valve 27, and the deposit adheres to the throttle valve 27 more. On the contrary, if the distance L is long, the EGR gas will not flow into the reverse flow region.
Since the GR gas becomes a non-uniform flow and flows downstream as it is, the mixing of the fresh air and the EGR gas does not proceed, and the variation between the cylinders of the EGR rate increases. That is, there is a trade-off relationship as shown in FIG. 7 between the deposit formation amount and the variation in EGR rate between cylinders, and it has been conventionally difficult to achieve both reduction in variation in EGR rate between cylinders and prevention of deposit formation. It was

On the other hand, in the present invention, the fresh air main flow velocity is the highest, and the fresh air and the EGR gas are merged at the position behind both the free ends 27a and 27b of the throttle valve 27 where the reverse flow region does not occur. Intake pipe 2 with fresh air and EGR gas
Since the spiral flow in the downstream direction of the inner circumference of No. 3 is mixed and mixed, the distance from the throttle valve 27 to the most upstream branch pipe 25 is extended, and the variation in EGR rate between cylinders can be reduced.

Moreover, since the EGR gas is introduced from the circumferential tangential direction of the cross section of the intake pipe 23, the EGR gas does not directly enter the backflow region downstream of the throttle valve 27 and the deposit formation on the throttle valve 27 is sufficiently prevented. To be done.

Further, by setting the distance Lb of the EGR gas introduction port 35 from the throttle valve 27 to be shorter than the distance La of the EGR gas introduction port 34 from the throttle valve 27, the EGR introduction port behind the forward tilted free end 27b. Three
5 to the most upstream side branch pipe 25, the EG
It is possible to lengthen the time when the R gas and fresh air are mixed.
When the intake pipe 23 and the collector 24 do not have a bend, the backflow region generated downstream of the rear surface of the throttle valve 27 is large behind the rearward tilt free end 27a and small behind the front tilt free end 27b. Even if the EGR gas introduction port 35 behind the tilted free end 27b is moved upstream, the EGR gas does not enter the reverse flow region.

Next, the second embodiment will be described.

FIG. 8 is an explanatory view of the EGR gas inlet. Here, the downstream angles (lead angles) of the two EGR gas inlets 34 and 35 are set to different values, and specifically, the EGR gas inlets 35 arranged behind the forward tilted free end 27b are set. The downstream direction angle θb is defined as the downstream direction angle θ of the EGR gas introduction port 34 disposed behind the rearward tilted free end 27a.
It is smaller than a.

As a result, the EG behind the forward tilted free end 27b is
The pitch (one turn) of the spiral flow from the R gas inlet 35 is reduced, and the length of the spiral flow can be increased.

Therefore, it becomes possible to make the EGR gas concentration distribution in the collector 24 more uniform, and
It is possible to reduce the variation in the rate between cylinders. Note that the spiral flow from the EGR gas inlet 35 may partially cross the backflow region when the inner circumference of the intake pipe 23 is substantially half-circulated, but at this time, mixing with fresh air has already progressed. Since the rich EGR gas does not directly enter the backflow region, deposit formation can be sufficiently suppressed.

Here, two EGR gas inlets 3 are provided.
Although only the function and effect when the downstream angles of 4 and 35 are set to different values have been described, as shown in FIG.
The distances of the R gas inlets 34 and 35 from the throttle valve may be set to different values. By setting the position and angle of the EGR gas inlet to the optimum ones according to the state of the fresh air mainstream, the state of the reverse flow region, etc., it is possible to further improve the variation reduction of the EGR rate and the prevention of deposit formation.

Next, a third embodiment will be described.

9 and 10 are explanatory views of the EGR gas inlet. As described above, when the intake pipe 23 including the throttle body 26 has a bend with respect to the collector 24 along the surface including the throttle valve axis, the flow outside the bend becomes stronger than the flow inside the bend. The backflow region that occurs downstream of the back surface of the throttle valve 27 becomes smaller outside the bend and becomes larger inside the bend.

Therefore, as shown in FIG. 9, the EGR gas introducing port 34 behind the rearward tilting free end 27a is arranged outside the bend, and the EGR gas introducing port 3 behind the forward tilting free end 27b is arranged.
If 5 is arranged from the inside of the bend, the backflow region will be small behind the rearward tilt free end 27a outside the bend, but EG will be behind the back tilt free end 27a where the backflow region is originally large.
The R gas introduction port 34 cannot be moved to the upstream too much. Further, since the backflow region becomes large behind the forward tilt free end 27b on the inside of the bend, the EGR gas inlet port 35
Can not be moved upstream.

Therefore, in the present invention, as shown in FIG. 10, the EGR gas introducing port 34 behind the rearward tilting free end 27a is disposed inside the bend, and the EG behind the front tilting free end 27b is arranged.
The R gas inlet 35 is arranged outside the bend. As a result, the EGR behind the rearward tilted free end 27a having a large backflow region is performed.
Since the position of the gas introduction port 34 is almost unchanged, the EGR gas introduction port 35 behind the forward tilted free end 27b outside the bend where the backflow region is small can be moved significantly upstream, so that the EGR gas introduction port 35 Of the EGR gas and the fresh air can be lengthened.

Therefore, it becomes possible to make the EGR gas concentration distribution in the collector 24 more uniform,
It is possible to reduce the variation in the rate. Further, since the backflow region becomes smaller outside the bend, the EGR gas does not enter the backflow region, and the deposit formation can be sufficiently suppressed.

Next, a fourth embodiment will be described.

11 and 12 are explanatory views of the EGR gas inlet. In this way, when the intake pipe 23 including the throttle body 26 has a bend with respect to the collector 24 along a plane orthogonal to the throttle valve axis, fresh air flows from the inside of the bend to the outside of the bend. Becomes stronger, the backflow region that occurs downstream of the rear surface of the throttle valve 27 becomes smaller inside the bend.

For this reason, as shown in FIG. 11, when the throttle valve 27 is arranged so that the free end outside the bend becomes the forward tilt free end 27b, the forward tilt free end 27b.
From this, the flow from the rearward tilted free end 27a becomes weak and the backflow region becomes large behind the forward tilted free end 27b, so the EGR gas introduction port 35 behind the tilted free end 27b cannot be moved to the upstream side. .

Therefore, in the present invention, as shown in FIG. 12, the throttle valve 27 is arranged so that the free end inside the bend becomes the forward tilt free end 27b. This allows
The main flow from the forward tilt free end 27b flows toward the outside of the bend, and the backflow region behind the forward tilt free end 27b becomes smaller. Therefore, the EGR gas introduction port 35 behind the forward tilt free end 27b can be moved upstream. Therefore, the distance L from the throttle valve 27 to the EGR gas introduction port 35 can be shortened.

Therefore, since the spiral flow from the EGR gas inlet 35 to the most upstream side branch pipe 25 becomes long, it becomes possible to make the EGR gas concentration distribution in the collector 24 more uniform, and the cylinder having the EGR rate. It is possible to reduce the variation between them. Further, since it is possible to suppress the EGR gas from flowing into the reverse flow region, it is possible to sufficiently suppress the formation of deposits on the throttle valve.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is an explanatory diagram of an EGR gas introduction port thereof.

FIG. 3 is an explanatory view of the EGR gas inlet of the same.

FIG. 4 Fresh air and EG downstream of the throttle valve
It is a figure which shows the flow of R gas.

FIG. 5 is a diagram showing the flow of fresh air and EGR gas downstream of the throttle valve.

FIG. 6 is an explanatory diagram of a backflow region that occurs downstream of the rear surface of the throttle valve.

FIG. 7 is a characteristic diagram of inter-cylinder variations in EGR rate and deposit formation amount.

FIG. 8 is an explanatory diagram of an EGR gas introduction port of the second embodiment.

FIG. 9 is an explanatory diagram of an EGR gas inlet of the third embodiment.

FIG. 10 is an explanatory view of the EGR gas inlet of the same.

FIG. 11 is an explanatory diagram of an EGR gas inlet of the fourth embodiment.

FIG. 12 is an explanatory view of the EGR gas inlet of the same.

FIG. 13 is a partial cross-sectional view of a conventional example.

FIG. 14 is a partial perspective view of another conventional example.

FIG. 15 is a schematic configuration diagram of still another conventional example.

[Explanation of symbols]

20 engine 23 Intake pipe 24 collectors 25 branch pipe 26 Throttle body 27 Throttle valve 27a Free tilt end 27b Forward tilt free end 30 exhaust pipe 31 EGR passage (external return passage) 32, 33 passage 34, 35 EGR gas inlet

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Junichi Kawashima 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) Reference JP-A-5-223016 (JP, A) JP-A-62- 247166 (JP, A) JP-A-8-319900 (JP, A) Actually developed 55-102056 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 25/07 580 F02M 35/10 311

Claims (5)

(57) [Claims] 1. An intake system having a throttle valve interposed upstream of an intake pipe having a branch pipe connected to each cylinder and a collector, and an EGR gas is introduced from an exhaust system via an external return passage to the rear of the intake system throttle valve. In the exhaust gas recirculation device for the engine that is introduced into the intake pipe upstream of the collector, a pair of EGR gas introduction ports from the external recirculation passage to the intake pipe are
Each of them is arranged behind both free ends of the throttle valve and from the tangential direction of the circumference of the intake pipe cross section, and is opened so that the inflow directions are opposite to each other. Is inclined in the downstream direction by at least one of the two EGR gas inlets from the throttle valve, and at least one of the downstream facing angle is set to a different value. 2. The distance from the throttle valve to the EGR gas introduction port provided at the rear of the forward tilt free end of the throttle valve, the distance from the throttle valve of the EGR gas introduction port provided at the rear of the backward tilt free end. The exhaust gas recirculation device for an engine according to claim 1, wherein the exhaust gas recirculation device is shorter than the above. 3. The downstream angle of the EGR gas introduction port provided behind the forward tilt free end of the throttle valve is made smaller than the downstream angle of the EGR gas introduction port provided behind the backward tilt free end. The exhaust gas recirculation device for an engine according to claim 1 or 2, characterized in that. 4. An EGR gas introduction port disposed at the rear of the forward tilted free end of the throttle valve when the intake pipe including the throttle body has a bend along the surface including the throttle valve axis with respect to the collector. 4. An EGR gas introduction port, which is arranged on the outside of the bend, and an EGR gas introduction port, which is arranged on the rear side of the rearward tilting free end, is arranged on the inside of the bend. Exhaust gas recirculation system for engines. 5. When the intake pipe including the throttle body has a bend with respect to the collector along a plane orthogonal to the throttle valve axis, the free end of the throttle valve inside the bend becomes the forward tilted free end. The exhaust gas recirculation device for an engine according to any one of claims 1 to 4, wherein the throttle valve is arranged as described above.