JP2000008970A - Exhaust gas recirculation system for internal combustion engine - Google Patents

Abstract

(57) [PROBLEMS] To improve the performance of distributing EGR gas to each cylinder of an internal combustion engine and to prevent backflow of gas to a throttle valve, and particularly to efficiently generate a swirling flow. Aim. SOLUTION: An intake system provided with a throttle valve 27 is provided upstream of an intake pipe 23 having a branch pipe 25 connected to each cylinder and a collector 24, and EGR gas is supplied from an exhaust system through an EGR passage 31 to the intake system. Throttle valve 27
It is introduced into the intake pipe 23 downstream and upstream of the collector 24. Semi-annular EGR passage 32 arranged in the circumferential direction of intake pipe 23
EGR gas is introduced through the EGR passage 31 into the
The GR passage 32 and the intake pipe 23 are connected to each other by a slit-shaped opening 33.
Connect with. Thereby, the swirling motion is given to the EGR gas introduced from the slit-shaped opening 33 to promote the mixing with the fresh air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas recirculation device (EGR device) for an internal combustion engine.

[0002]

2. Description of the Related Art A conventional exhaust gas recirculation system for an internal combustion engine is disclosed, for example, in Japanese Utility Model Laid-Open No. 3-114563 shown in FIG. 13, Japanese Patent Application Laid-Open No. 8-218949 shown in FIG. And Japanese Patent No. 218949.

[0003] Referring to FIG. 13, the EGR gas from the gas introduction passage 1 is supplied from two horizontally opposed openings 4 through gas guide grooves 3 provided around the intake pipe 2. Introduced into the pipe 2, fresh air and EG
Mix R gas.

In FIG. 14, EGR is provided around the intake pipe 5.
By forming an annular passage 6 into which gas is introduced and introducing EGR gas into the intake pipe 5 through a plurality of holes 7 connecting the wall of the intake pipe 5 and the annular path 6, fresh air and EGR gas are introduced. Mix. Each of these aims at equalizing the mixing of the EGR gas and reducing the variation in the exhaust gas recirculation rate between the cylinders.

In FIG. 15, a second surge tank 12 is provided in the intake passage 10 downstream of the first surge tank 11, and an EGR gas introduction section 13 is arranged in the second surge tank 12. . By introducing the EGR gas into the second surge tank 13 at a position distant from the throttle valve 14 as described above, the deterioration component (deposit) of the exhaust gas is prevented from adhering to the throttle valve 14.

[0006]

However, in such a conventional exhaust gas recirculation device, the exhaust gas to the intake pipe is not provided.
The GR gas introduction part is not always located at the optimum position and direction. For example, only the EGR gas is introduced from the hole 7 provided on the wall surface of the intake pipe 5 as shown in FIG. 14, or in the horizontal direction as shown in FIG. The introduction of EGR gas only from the opposing opening 4 causes the EGR gas to be partially biased, failing to mix the EGR gas and fresh air satisfactorily. The one in FIG.
The flow state of the fresh air by the throttle valve greatly affects the mixing of the EGR gas and the fresh air and the adhesion of the deposit to the throttle valve. In the case where the EGR gas is introduced into the second surge tank 13 as shown in FIG. 15, it is difficult to distribute the EGR gas from the surge tank 13 to each cylinder evenly.

For this reason, when a large amount of EGR is performed, mixing of the EGR gas and fresh air becomes insufficient, and as a result, the EGR rate varies among the cylinders, deteriorating the stability of the engine and reducing the emission. This leads to an increase in fuel economy. Except for those shown in FIG. 15, there is a concern that the control of the intake air amount and the like may be deteriorated due to the formation of the deposit on the throttle valve.

The present applicant has proposed Japanese Patent Application No. 9-142381 in order to improve these problems, but the present invention seeks to further improve the present invention.

That is, according to the present invention, E
By providing a swirling flow to the GR gas and introducing the EGR gas from a wide area to promote mixing with fresh air, the EG
An object of the present invention is to improve the performance of distributing R gas to each cylinder and prevent backflow of EGR gas to a throttle valve.

[0010]

According to a first aspect of the present invention, there is provided 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 exhaust recirculation passage from the exhaust system. In an exhaust gas recirculation system for an internal combustion engine that introduces EGR gas into an intake pipe downstream of a throttle valve and upstream of a collector via an intake system, a semi-circular EGR introduction path disposed on the outer periphery of the intake pipe is provided. The recirculation passage was connected, and the EGR introduction passage was communicated with the intake pipe through a slit-shaped opening extending over substantially half a circumference.

According to a second aspect of the present invention, in the first aspect, the slit-shaped opening is opened into the intake pipe at a predetermined angle with respect to the fresh air flow direction.

[0013] In a third aspect based on the first or second aspect, the cross-sectional area of the EGR introduction path gradually decreases toward the downstream side in the flow direction of the EGR gas flow.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the length of the cross-sectional area changing section in which the cross-sectional area of the EGR introduction path decreases substantially matches the length of the slit-shaped opening. I did it.

In a fifth aspect based on any one of the first to fourth aspects, the EGR introduction path is provided in at least one of a vertical direction substantially perpendicular to a valve axis of the throttle valve.

In a sixth aspect based on the fifth aspect, the EGR introduction path is provided in the intake pipe on the free front end side of the throttle valve.

In a seventh aspect based on the fifth aspect, the EGR introduction path is provided at one location on the circumference of the intake pipe in a vertical direction substantially perpendicular to the valve axis of the throttle valve.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, a midpoint of the slit-shaped opening in a circumferential direction of the intake pipe is orthogonal to a valve axis center line of the throttle valve, The valve body is provided on the upstream side of the flow of the EGR gas with respect to a valve center line that bisects the valve body.

[0018]

According to the first aspect of the present invention, a semi-annular EGR introduction passage disposed on the outer periphery of the intake pipe is provided.
Since the EGR gas is introduced into the intake pipe from the slit-shaped opening extending over substantially half the circumference of the introduction path, a swirling flow corresponding to the length of the slit-shaped opening is formed.
Mixing of gas and fresh air can be further promoted, and the performance of distributing gas to each cylinder is improved.

In the second aspect of the present invention, since the slit-shaped opening is opened into the intake pipe at a predetermined angle with respect to the fresh air flow direction, a flow velocity vector downstream of the intake pipe is defined, and the throttle valve section is provided. Backflow can be prevented.

According to the third aspect of the present invention, the cross-sectional area of the EGR introduction passage gradually decreases toward the downstream side in the flow direction of the EGR gas flow, so that the EGR jetted from the slit with the decrease in the cross-sectional area. The gas amount becomes substantially constant over the entire slit-shaped opening, and the EGR gas having the same flow velocity can be jetted into the intake pipe, so that the mixing of the EGR gas and fresh air can be further promoted.

According to the fourth aspect of the invention, since the length of the cross-sectional area changing section where the cross-sectional area of the EGR introduction passage decreases is substantially equal to the length of the slit-shaped opening, the mixing of the EGR gas and fresh air is improved. Can be further promoted.

In the fifth aspect, the EGR introduction path is provided in at least one of the vertical direction substantially perpendicular to the valve axis of the throttle valve, so that the EGR gas can be jetted into the main flow, so that the EGR gas is efficiently supplied. And fresh air can be mixed.

In the sixth aspect of the present invention, since the EGR introduction path is provided in the intake pipe at the free front end of the throttle valve, EGR gas can be injected into the main flow, so that EGR gas and fresh air can be efficiently supplied. Can be mixed.

In the seventh aspect of the present invention, the EGR introduction path is provided at one place on each of the valve shaft of the throttle valve and the circumference of the intake pipe in the vertical direction, so that the EGR gas and fresh air can be more efficiently mixed. it can.

In the eighth invention, the midpoint of the slit-shaped opening in the circumferential direction of the intake pipe is perpendicular to the centerline of the valve axis of the throttle valve, and the centerline of the valve body halves the valve body. Thus, since the EGR gas is provided on the upstream side of the flow of the EGR gas, it is possible to prevent the EGR gas from being caught in the reverse flow region of the intake air, which is most developed at the valve shaft of the throttle valve, and to suppress the EGR gas from flowing back to the throttle valve. can do.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the basic configuration of the first embodiment.
The engine body 20 has an intake pipe 23 and a collector 24 on the intake side.
And intake manifold 21 comprising intake side branch pipe 25
The exhaust side is connected to an exhaust manifold 22 including an exhaust side branch pipe 28 and an exhaust pipe 30.
An EGR introduction path 32 is provided on the outer periphery of the intake pipe 23 of the intake manifold 21, and as shown in FIG. 2, the EGR introduction path 32 communicates with the intake pipe 23 through a slit-shaped opening 33. The EGR introduction passage 32 communicates with the exhaust pipe 30 via the EGR passage 31. EGR introduction path 3 of intake pipe 23
A throttle body 26 having a butterfly type throttle valve 27 composed of a valve shaft 27a and a valve body 27b rotatably attached to the intake pipe 23 is disposed upstream of the opening 2.

FIG. 3 is a sectional view in the fresh air flow direction, and FIG.
Shows a cross-sectional view in the EGR gas flow direction.

Here, the EGR introduction passage 32 is located on the downstream side of the throttle valve 27, but when opening and closing around the valve shaft 27a, the front tilting free end 27c side of the valve body 27b (when the valve body 27b is tilted, the valve shaft 27). (On the upstream side of 27a), is formed in a semi-annular shape over substantially half a circumference along the outer wall of the intake pipe 23, and the bottom thereof is connected to the intake pipe 23 through a slit-shaped opening 33. . The cross section of the opening 33 is such that the inner wall on the downstream side of the EGR introduction passage 32 is inclined by a predetermined angle θ with respect to the fresh air flow direction of the intake pipe 23, and the opening 33 is oriented in the fresh air flow direction in FIG.
As shown in the figure, the inner wall is opened to the intake pipe 23 with an opening width of a certain dimension L.

The cross-sectional area S of the EGR introduction passage 32 is substantially equal to the length of the slit-shaped opening 33 in the cross-sectional area α of the EGR introduction passage 32, as shown in FIGS. And decreases substantially proportionally toward the downstream of the flow. However, the opening width L to the intake pipe 23 is constant also in the cross-sectional area change section α.

Next, the operation will be described.

FIG. 7 shows a normal operation region and an EGR region which are represented by the relationship between the engine speed and the throttle opening. The area where the EGR is used in the normal operation area is an area excluding a high load area near the throttle fully open and a low load area near the idle.

The EGR gas that has passed through the EGR passage 31 passes through the EGR introduction passage 32 and passes through the slit-shaped opening 3.
3 is uniformly injected into the intake pipe 23 from almost the entire region.
Since these EGR gas flows have a uniform angular momentum with respect to the circumferential direction of the intake pipe 23, a swirl flow corresponding to the length of the slit-shaped opening 33 is formed, and the swirl flow is Mixing of EGR gas and fresh air can be further promoted.

Next, as shown in FIG. 3, since the slit-shaped opening 33 has a predetermined angle with respect to the fresh air flow direction, that is, is inclined toward the downstream side, the intake pipe 23
The flow velocity vector to the downstream is defined, and the backflow to the upstream throttle valve 27 can be prevented. Further, since the flow of the EGR gas is a blowout flow from the nozzle-shaped opening 33, the directionality is accurately reflected according to the angle.
Therefore, the mixing of the EGR gas and fresh air can be further promoted.

As shown in FIG. 4, the cross-sectional area of the EGR introduction path 32 decreases substantially proportionally in the cross-sectional area change section α of the EGR introduction path 32 (the volume per unit distance of the passage decreases at a constant rate). A uniform amount of EGR gas can be ejected into the intake pipe 23 over the entire slit-shaped opening 33, and the length β of the cross-sectional area change section α and the circle of the intake pipe 23 of the slit-shaped opening 33 can be increased. Since the lengths on the circumference substantially match, the mixing of the EGR gas and fresh air can be further promoted. In addition, the difference in the collector shape due to the difference in the engine model and the model of the engine mounted,
Since the influence of the GR distribution characteristics is small, there is an advantage that the shape can be easily selected and the horizontal deployment to each model of the engine is easy. In addition, there is also an effect of reducing variations in EGR distribution caused by variations in shape at the time of production, operating conditions of the engine, and the like.

8 and 9 show the flow downstream of the throttle valve 27 in the intake pipe 23. In contrast to the main flow passing through the opening of the throttle valve 27, the flow circulates behind the throttle valve 27. Although a basin exists, in the present invention, the slit-shaped opening 3 from which the EGR gas is jetted out
3 is provided on the upper or lower part of the valve body 27b, particularly on the side of the forward inclined free end 27c, so that the EGR gas can be jetted into the upper or lower mainstream as shown in FIG. EGR gas and fresh air can be mixed. Further, since the slit-shaped opening 33 is provided at a position separated by a predetermined distance x in the downstream direction of the fresh air flow with respect to the valve shaft 27a of the throttle valve 27, an area for minimizing the influence of the reverse flow area as shown in FIG. Since the EGR gas can be jetted out, the backflow can be reliably avoided.

FIG. 10 shows a second embodiment. This embodiment is different from the first embodiment in that the midpoint P of the slit-shaped opening 33 in the circumferential direction of the intake pipe is different from the throttle valve 27 in FIG.
Perpendicular to the center line of the valve shaft 27a of
It is moved to the upstream side of the EGR introduction path 32 with respect to the valve center line which is equally divided. As a result, it is possible to prevent the EGR gas from being caught in the reverse flow region of the intake air, which is most developed at the valve shaft 27a of the throttle valve 27, and to suppress the reverse flow of the EGR gas to the throttle valve 27.

FIG. 11 shows a third embodiment. In the present embodiment, two EGRs are provided at opposed positions on the outer periphery of the intake pipe 23.
Passages 31 and 35 are provided, each of which has a forward leaning free end 27c and a backward leaning free end 27 of a valve body 27b of the throttle valve 27.
The intake pipe 23 is provided through a slit 33 provided on each of the d-sides.
Communicate with In this manner, the EGR gas ejection region can be expanded all around, and EG
Since the R gas can be introduced substantially uniformly, the EGR gas and fresh air can be more efficiently mixed.

FIG. 12 shows a comparison between the conventional example of the variation of the EGR rate among the cylinders and the present invention. The present invention is an improvement over the prior art and Japanese Patent Application No. 9-142381. It can be seen that the EGR rate is made uniform.

[Brief description of the drawings]

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

FIG. 2 is a stereoscopic perspective view.

FIG. 3 is a sectional view in a fresh air flow direction.

FIG. 4 is a cross-sectional view in the EGR gas flow direction.

FIG. 5 is a characteristic diagram showing a relationship between a distance β from a cross-sectional area reduction start point of the EGR passage and a cross-sectional area S of the EGR passage.

FIG. 6 is a characteristic diagram showing a relationship between a distance β from a cross-sectional area reduction start point of an EGR passage and an opening width L of a slit-shaped opening.

FIG. 7 is a characteristic diagram showing an EGR region.

FIG. 8 is a plan view showing a flow downstream of the throttle valve.

FIG. 9 is a side view showing the flow downstream of the throttle valve.

FIG. 10 is an explanatory diagram of the second embodiment.

FIG. 11 is an explanatory diagram of the third embodiment.

FIG. 12 is a comparison diagram of the variation of the EGR rate between the conventional example and each cylinder of the present invention.

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

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

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

DESCRIPTION OF SYMBOLS 20 Engine 23 Intake pipe 24 Collector 25 Intake side branch pipe 26 Throttle body 27 Throttle valve 27a Valve shaft 27b Valve body 27c Forward free end 27d Back free end 30 Exhaust pipe 31 EGR passage (Exhaust recirculation passage) 32 EGR introduction path 33 Opening 34 EGR introduction path 35 EGR passage (exhaust recirculation passage)

Claims (8)

[Claims] An intake system having a throttle valve is provided upstream of an intake pipe having a branch pipe and a collector connected to each cylinder, and EGR gas is supplied from an exhaust system through an exhaust gas recirculation passage to a downstream of a throttle valve of the intake system. And in the exhaust gas recirculation device of the internal combustion engine introduced into the intake pipe upstream of the collector,
A semi-annular EGR introduction path provided on the outer periphery of the intake pipe is provided,
An exhaust recirculation passage is connected to this EGR introduction passage,
An exhaust gas recirculation device for an internal combustion engine, wherein a GR introduction path is communicated with an intake pipe through a slit-shaped opening that extends over substantially half a circumference. 2. An exhaust gas recirculation system for an internal combustion engine according to claim 1, wherein said slit-shaped opening is opened in the intake pipe at a predetermined angle with respect to a fresh air flow direction. . 3. The internal combustion engine according to claim 1, wherein the cross-sectional area of the EGR introduction passage decreases at a substantially constant decreasing rate toward the downstream side in the flow direction of the EGR gas flow. Engine exhaust gas recirculation device. 4. The apparatus according to claim 1, wherein the length of the cross-sectional area where the cross-sectional area of the EGR introduction path decreases is substantially equal to the length of the slit-shaped opening. An exhaust gas recirculation device for an internal combustion engine according to claim 1. 5. The exhaust gas of an internal combustion engine according to claim 1, wherein said EGR introduction path is provided in at least one of a vertical direction substantially perpendicular to a valve axis of a throttle valve. Reflux device. 6. An exhaust gas recirculation system for an internal combustion engine according to claim 5, wherein said EGR introduction path is provided in an intake pipe on a free front end side of a throttle valve. 7. The exhaust gas recirculation of an internal combustion engine according to claim 5, wherein said EGR introduction path is provided at one place on the circumference of the intake pipe in a vertical direction substantially perpendicular to the valve axis of the throttle valve. apparatus. 8. A midpoint of the slit-shaped opening in a circumferential direction of the intake pipe is orthogonal to a centerline of a valve shaft of the throttle valve, and is located at a position E.sub.
The exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 7, wherein the exhaust gas recirculation device is provided upstream of a flow of the GR gas.