JP2003083050A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine for recirculating unburnt HC components in exhaust gas adsorbed by an HC adsorbent via a recirculating connecting a bypass exhaust passage to the upstream position of a catalyst device, having a simply constructed takeoff port for the recirculating pipe on the side of the bypass exhaust passage. SOLUTION: The exhaust emission control device for the internal combustion engine for recirculating the unburnt HC components in the exhaust gas adsorbed by the HC adsorbent 64 via an EGR pipe (the recirculating pipe) 72 connecting the bypass exhaust passage 54a to the upstream position of the catalyst device comprises the takeoff port 72b for the EGR pipe 72 integrally formed with (a flange 50b of a selector valve body 50 and) a flange 52a of a branch pipe 52 and thus simply constructed to improve working efficiency, avoid a cost increase and provide improved maintenance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, a catalyst device is provided in an exhaust system to remove HC, NOx, and CO components in exhaust gas for purification, but the catalyst device is not activated even when the engine is cold started. At this time, unburned components, particularly unburned HC components, are discharged as they are outside the engine.

Therefore, in Japanese Patent Laid-Open No. 10-153112, etc., an exhaust pipe of an internal combustion engine is branched downstream of a catalyst device, and a bypass exhaust passage opened / closed via a switching valve is provided to provide a zeolite adsorbent or the like. When the catalyst device is not activated by accommodating the adsorbing means, the bypass exhaust passage is opened to introduce the exhaust gas at the time of engine start to adsorb unburned components, and the unburned component adsorbed after the catalyst device is activated. An exhaust gas purification apparatus has been proposed in which components are desorbed and recirculated to an intake system upstream of a catalyst device via a recirculation pipe (EGR passage), reburned, and purified by the catalyst device while being discharged to the outside of the engine.

Such a reflux pipe is specifically described in Japanese Patent Laid-Open No. 2
As described in Japanese Patent Laid-Open No. 000-200720, the pipe is formed to extend to the bypass exhaust passage.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the structure as described in Japanese Patent Publication No. 200720, in practice, a work such as inserting a pipe of a separate member into a cylindrical case in which a bypass exhaust passage is formed and joining the pipe is necessary for the outlet. As a result, work efficiency is reduced and cost is increased. In addition, increasing the number of joints is not preferable because it increases the number of places where leakage occurs.

Furthermore, the exhaust gas purification unit cannot be easily removed from the branch pipe (and the upstream exhaust pipe that is flange-joined thereto), which is inconvenient in terms of maintainability.

Therefore, the present invention is to eliminate the above-mentioned inconvenience, and the unburned HC component in the exhaust gas adsorbed to the HC adsorbent through the reflux pipe connecting the bypass exhaust passage to the upstream position of the catalyst device. In an exhaust gas purification device for an internal combustion engine that recirculates the exhaust gas, an exhaust gas purification device for an internal combustion engine in which a take-out port of a recirculation pipe on a bypass exhaust passage side is simply configured.

[0008]

In order to achieve the above object, according to the present invention, in claim 1, an exhaust pipe for discharging exhaust gas of an internal combustion engine to an outside of the engine is branched at a position downstream of a catalyst device. The pipes are connected via a flange, a main exhaust passage and a bypass exhaust passage for accommodating the HC adsorbent are formed in the branch pipe, and the exhaust pipe is switched to select the main exhaust passage and the bypass exhaust passage through a switching valve. Of the unburned HC component in the exhaust gas adsorbed by the HC adsorbent through a recirculation pipe that connects the bypass exhaust passage to the upstream position of the catalyst device and recirculates the unburned HC component to the upstream side of the catalyst device. In an exhaust gas purification device for an internal combustion engine, the outlet of the reflux pipe is formed integrally with the flange of the branch pipe, and more specifically, the outlet of the reflux pipe is switched. It was composed as integrally formed on the flange of the branch pipe through the flange of the body.

Since the take-out port of the return pipe is formed integrally with the flange of the branch pipe, the take-out port of the return pipe on the bypass exhaust passage side can be simply constructed, and as described above, it is a separate member. The work of inserting and joining the pipe of (1) into the cylindrical case in which the bypass exhaust passage is formed is not required, and the work efficiency is improved and the cost increase can be avoided. Furthermore, since the number of joints does not increase, the number of places where leakage occurs does not increase.

Further, since the outlet of the reflux pipe is formed integrally with the flange of the branch pipe, the bypass pipe in which the bypass exhaust passage is formed (including the cylindrical case) is located on the upstream exhaust pipe side. It is possible to easily remove from the, and maintainability can be improved.

According to a second aspect of the present invention, the bypass passage is airtightly fixed to the opening formed in the flange of the branch pipe, and a hole is formed in the vicinity thereof at a position corresponding to the outlet. Therefore, the reflux pipe is configured to be connected to the bypass exhaust passage.

The bypass passage is airtightly fixed to the opening formed in the flange of the branch pipe, and a hole is formed in the vicinity of the opening corresponding to the outlet, so that the return passage is connected to the bypass exhaust passage. Since it is configured so as to be simpler in structure, the cost increase can be further avoided, and the branch pipe can be removed more easily from the upstream exhaust pipe side, further improving the maintainability. be able to.

[0013]

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

FIG. 1 is a side view generally showing an exhaust emission control system for an internal combustion engine according to one embodiment of the present invention. In FIG. 1, arrow A indicates the gravity axis.

In the drawing, reference numeral 10 indicates an OHC in-line 4-cylinder internal combustion engine (hereinafter referred to as "engine", only one cylinder is shown). While the flow rate of the air sucked from the intake pipe (intake passage) 12 is adjusted by the throttle valve 14,
Two intake valves 18 (1 through the intake manifold 16
(Only one is shown) is sent to each cylinder.

An injector (fuel injection valve) 20 is provided in the vicinity of the intake valve 18 of each cylinder to inject fuel. The air-fuel mixture injected and integrated with the intake air is sucked into the combustion chamber 24 of the cylinder in the intake stroke, is compressed in the compression stroke, is ignited through the ignition plug 26, and burns, and the piston 28 is moved downward in the drawing. Drive to.

The exhaust gas (exhaust gas) after combustion is discharged to an exhaust pipe (exhaust passage) 38 through two exhaust valves (only one is shown) 30 and an exhaust manifold 32, and is provided under the floor of a vehicle (not shown). , A first catalyst bed (three-way catalyst) 40 and a second catalyst bed (three-way catalyst) 42
4 and is further discharged into the atmosphere via a rear end portion (only a part of which is indicated by reference numeral 46) including a silencer and a tail pipe (both not shown) located further downstream.

The engine 10 has a so-called variable valve timing mechanism 48. However, the variable valve timing mechanism 48 is described in, for example, Japanese Unexamined Patent Publication No. 275043/1990, so a detailed description thereof will be omitted.

The exhaust pipe 38 is connected to the switching valve body 50 downstream of the catalyst device 44, and the switching valve body 50 is connected to the branch pipe 52. 2 is an enlarged sectional view of the switching valve body 50 and the branch pipe 52, and FIG. 3 is a sectional view taken along line III-III of FIG.

As shown in FIG. 2, the exhaust pipe 38 and the switching valve body 50 are constructed separately, and the flanges 38a, 5
0a is bolted and connected, and the switching valve body 50 and the branch pipe 52 are also formed separately, and the flanges 50b and 52a are bolted and connected. further,
The branch pipe 52 is connected to the rear end portion 46 by bolting flanges 52b and 46a.

The branch pipe 52 has a structure as shown in FIG. That is, the branch pipe 52 starts from the inlet 52c shown in FIG. 3 and has a small diameter first cylindrical case 54 passing through the center and the inlet 52d shown in FIG. 3 and the first cylindrical case 54.
And a second cylindrical case 56 having a diameter larger than that of the first cylindrical case 54, which is concentrically formed so as to surround the.

That is, an annular flow path is formed in the second cylindrical case 56 in a sectional view. First cylindrical case 54
Both the second cylindrical case 56 and the second cylindrical case 56 are airtightly fixed to the openings formed in the flanges 52a and 52b, respectively. As shown by the broken line in FIG. 3, the first cylindrical case 54 has an elliptical shape in the portion fixed to the flange 52a.

The switching valve body 50 has a first
The cylindrical case 54 is connected to the second cylindrical case 56 via the inlet 52c, and the other end is connected to the second cylindrical case 56 via the inlet 52d. Accordingly, as the exhaust gas passage, in the downstream of the switching valve body 50, the main exhaust passage 56a passing through the annular flow passage of the second cylindrical case 56.
And a bypass exhaust passage 54a passing through a circular space formed inside the first cylindrical case 54 is formed. The exhaust gas (exhaust gas) discharged from the combustion chamber 24 flows through one of the exhaust passages.

The switching valve body 50 includes a switching valve 60. The switching valve 60 is provided with a planar circular valve disc 60a and a shaft 60c fixed thereto via a C-shaped arm 60b in a side view. The shaft 60c is connected to a valve operating mechanism (not shown), and the valve operating mechanism is connected to a position downstream of the throttle valve 14 via a negative pressure introducing passage (not shown). An electromagnetic solenoid valve (TRP
V. (Not shown) is provided, and TRPV is turned on (excitation)
Then, the negative pressure introducing passage is opened to introduce the negative pressure.

When the TRPV is turned on and a negative pressure is introduced, the valve disc 60a is rotated from the position shown in FIG. 2, and the first valve seat of the switching valve body 50 is continuous with the second cylindrical case 56. When the second cylindrical case 56 (main exhaust passage 56a) is closed by abutting 50c and the TRPV is turned off and the negative pressure introduction passage is opened to the atmosphere, the valve disc 60a causes a return spring (not shown). 2 returns to the position shown in FIG. 2 and contacts the second valve seat 50d of the switching valve body 50 to close the first cylindrical case 54 (bypass exhaust passage 54a).

In the bypass exhaust passage 54a formed in the first cylindrical case 54, an HC adsorbent (HC adsorbing catalyst) 64 supported by a metal carrier (honeycomb body) is arranged. That is, as shown in FIG. 3, the first cylindrical case 54
An HC adsorbent 64 having a circular cross section is similarly arranged (accommodated) inside the.

As described above, the main exhaust passage 56a formed in the exhaust pipe 38, more specifically in the second cylindrical case 56 continuous with the exhaust pipe 38, surrounds the first cylindrical case 54 forming the bypass exhaust passage 54a. As described above, the HC adsorbent 64, which is adjacent to the first cylindrical case 54 and accommodated therein, is brought into thermal contact with the main exhaust passage 56a,
It is configured so that the temperature rise of the HC adsorbent 64 is effectively promoted to allow the unburned components to be desorbed at an early stage, and to be quickly returned to the intake system upstream of the catalyst device 44.

The HC adsorbent 64 is made of zeolite, which is a crystalline silicate previously proposed by the present applicant in Japanese Patent Laid-Open No. 8-71427. The type of the HC adsorbent having heat resistance is not limited, but in this embodiment, it is composed of a mixture of Y-type, Ga-MFI, and ferrierite zeolites. 338
A metal honeycomb core body (carrier) formed by spirally winding and stacking thin metal plate materials as proposed in Japanese Patent No. 75 is used.

This crystalline silicate has a heat resistance temperature of 900.
Exhibits excellent high-temperature durability at temperatures between ℃ and 1000 ℃ compared to activated carbon. The HC adsorbent 64 adsorbs unburned HC components when the exhaust system temperature is lower than 100 ° C.
The unburned HC component adsorbed at 0 ° C to 250 ° C is desorbed.
The adsorption or desorption temperatures of HC components are
It depends on the species of the ingredient.

In the first cylindrical case 54, the HC adsorbent 6
Five holes 66 are formed at 72-degree intervals downstream (on the side near the rear end 46) of the arrangement position of No. 4, so that the main exhaust passage 56a and the bypass exhaust passage 54a communicate (merge) with each other through the hole 66. To be

Returning to the explanation of FIG. 1, the first cylindrical case 5
4 (bypass exhaust passage 54a) is connected to an EGR pipe (exhaust gas recirculation pipe or recirculation pipe) 72 on the upstream side (the side close to the switching valve body 50).

The EGR pipe 72 is supported by the engine 10 by a support 76 projecting from the cylinder side surface of the engine 10 and fixed to the exhaust pipe 38 by a stay 78.
The catalyst device 44 extends along the side surface to reach the first cylindrical case 54, and is attached at the lower portion (in the gravity axis direction) position. A bellows-shaped portion 72a is provided in the middle of the EGR pipe 72.
Is formed, and the EGR pipe 72 is expanded and contracted according to the exhaust pipe 38 expanding and contracting due to exhaust heat. Also, EGR
The pipe 72 includes the branch pipe 52 provided on the vehicle body side and the engine 1
Although the vibration system is mounted on the 0 side across different parts, the bellows-shaped part 72a also serves to absorb the vibration difference.

The outlet 72b of the EGR pipe 72 has a first
In the vicinity of the cylindrical case 54, as shown in FIG. 2, the switching valve body 50 is press-fitted into a hole 50b1 formed in the flange 50b of the switching valve body 50, and the periphery thereof is welded and fixed.
That is, the outlet 72b of the EGR pipe 72 is formed integrally with the flange 50b of the switching valve body 50.

The flange 52a of the branch pipe 52 has a
A first cylindrical case 54 forming a bypass exhaust passage 54a is airtightly fixed to an opening formed at a position corresponding to the inlet 52c shown in FIG. 3, and at a lower position in the vicinity thereof as shown in FIG. A hole 52a1 is formed at a position corresponding to the outlet 72b (hole 50b1), so that the EGR pipe 72 opens inside the first cylindrical case 54 through the hole 52a1, and the bypass exhaust passage 54a and the intake pipe 12 are formed. The downstream position of the throttle valve 14 is connected.

As a result, as described above, the work of inserting the separate pipe into the first cylindrical case 54 in which the bypass exhaust passage 54a is formed and welding is unnecessary, and the EGR on the bypass exhaust passage 54a side is eliminated. The take-out port 72b of the pipe 72 can be simply configured, cost increase can be avoided, and the number of joints does not increase.

Furthermore, the outlet 72b of the EGR pipe 72
Is formed integrally with the flange 50b of the switching valve body 50, the bypass exhaust passage 5
The branch pipe 52 in which 4a is formed (including the first cylindrical case 54) can be easily removed from the switching valve body 50 (and the upstream exhaust pipe 38 that is flange-joined thereto), which improves maintainability. be able to.

An EGR control valve (not shown) consisting of an electromagnetic solenoid valve is inserted at an appropriate position of the EGR pipe 72. When the EGR control valve is turned on (excited), E
The GR pipe 72 is opened, and the first cylindrical case 54 (bypass exhaust passage 54a) is connected to the intake system (intake pipe 12) on the upstream side of the catalyst device 44.

The operation of the above-described exhaust gas purification device will be briefly described below. When the catalyst device 44 is not activated after the engine 10 is started, the switching valve 60 is used.
The first cylindrical case 54 is opened via the
The cylindrical case 56 is closed, the exhaust gas is supplied to the bypass exhaust passage 54a, and unburned components such as HC in the exhaust gas are discharged to the HC.
It is adsorbed on the adsorbent 64. The exhaust gas after adsorbing the unburned components is released to the outside of the engine (atmosphere) through the rear end portion 46, the silencer and the like.

Then, when the catalyst device 44 is activated,
The first cylindrical case 54 is closed, the second cylindrical case 56 is opened, and the exhaust gas is discharged to the outside of the engine through the main exhaust passage 56a. At this time, the exhaust gas flowing through the main exhaust passage 56a raises the temperature of the HC adsorbent 64, and the unburned components adsorbed therein are desorbed.

Next, in a predetermined operating state, EGR
When (exhaust gas recirculation) is executed, the EGR control valve is turned on (excited), the first cylindrical case 54 (bypass exhaust passage 54a) is connected to the intake system upstream of the catalyst device 44,
The desorbed unburned components stored therein are returned to the intake system upstream of the catalyst device 44 via the EGR pipe 72. At this time, a part of the exhaust gas flowing through the main exhaust passage 56a is partially covered by the holes
6 to enter the bypass exhaust passage 54a to promote desorption and recirculation of unburned components.

Since the engine exhaust gas purifying apparatus according to this embodiment is constructed as described above, the pipe of another member is inserted into the first cylindrical case 54 in which the bypass exhaust passage 54a is formed as described in the prior art. Therefore, it is possible to avoid an increase in cost by eliminating the work of welding and the like, and the number of joints does not increase.

Further, the outlet 72b of the EGR pipe 72
Is formed integrally with the flange 50b of the switching valve body 50, the bypass exhaust passage 5
The branch pipe 52 in which 4a is formed (including the first cylindrical case 54) can be easily removed from the switching valve body 50 (and the upstream exhaust pipe 38 that is flange-joined thereto), which improves maintainability. be able to.

As described above, in the first embodiment, the branch pipe 52 is provided in the exhaust pipe 38 for discharging the exhaust gas of the internal combustion engine (engine 10) to the outside of the engine, downstream of the position where the catalyst device 44 is arranged. The flange 38a (50a, 50
b) and 52a, and the branch pipe 52
A bypass exhaust passage 54a for accommodating the main exhaust passage 56a and the HC adsorbent 64 is formed, and the exhaust pipe 38 is selectively connected to the main exhaust passage and the bypass exhaust passage via a switching valve 60. A recirculation pipe (EGR that connects the exhaust passage to an upstream position of the catalyst device).
In an exhaust gas purification apparatus for an internal combustion engine that recirculates unburned HC components in exhaust gas adsorbed by the HC adsorbent via a pipe 72) to the upstream side of the catalyst device, the outlet 72b of the recirculation pipe is connected to the branch pipe. The flange 52a of 52 is formed integrally (more specifically, via the flange 50b of the switching valve body 50).

The bypass passage 54a (more specifically, the first cylindrical case 54 in which the bypass exhaust passage 54a is formed) is airtightly fixed to the opening formed in the flange 52a of the branch pipe 52. At the same time, a hole 52a1 is formed in the vicinity thereof at a position corresponding to the outlet 72b, so that the reflux pipe is connected to the bypass exhaust passage.

In the above description, the EGR pipe 72 is integrally formed with the outlet 72b as shown in FIG. You may make it detachable with the said member using a screw etc.

Also, an example has been shown in which the switching valve 60 and the EGR pipe 72 are provided on the upstream side (the side close to the switching valve body 50) as the structure of the bypass exhaust passage, but the present invention is not limited to this, and Japanese Patent Laid-Open No. 10-159544.
Switching valve and EGR as described in the publication
This is also applicable to an example in which the pipe is provided on the downstream side (the side close to the rear end portion 46).

[0047]

According to the first aspect of the present invention, since the take-out port of the return pipe is formed integrally with the flange of the branch pipe, the take-out port of the return pipe on the bypass exhaust passage side is simply constructed. As described above, the work of inserting and joining the pipe of another member into the cylindrical case in which the bypass exhaust passage is formed as described above becomes unnecessary, and the work efficiency is improved and the cost increase can be avoided. it can. Furthermore, since the number of joints does not increase, the number of places where leakage occurs does not increase.

Further, since the outlet of the return pipe is formed integrally with the flange of the branch pipe, the branch pipe in which the bypass exhaust passage is formed (including the cylindrical case) is provided on the upstream exhaust pipe side. It is possible to easily remove from the, and maintainability can be improved.

According to the second aspect of the present invention, the bypass passage is airtightly fixed to the opening formed in the flange of the branch pipe, and a hole is formed in the vicinity thereof at a position corresponding to the takeout port. Since the recirculation passage is connected to the bypass exhaust passage, the structure can be further simplified and the cost increase can be better avoided, and the branch pipe can be removed more easily from the upstream exhaust pipe side. Therefore, the maintainability can be further improved.

[Brief description of drawings]

FIG. 1 is a side view generally showing an exhaust emission control system for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view of a switching valve body and a branch pipe in the device shown in FIG.

3 is a sectional view taken along line III-III in FIG.

[Explanation of symbols]

10 Internal combustion engine (engine) 12 Intake pipe 38 Exhaust pipe 38a flange 44 Catalytic device 50 switching valve body 50a flange 50b flange 52 Branch pipe 52a flange 52a1 hole 52b flange 54 First Cylindrical Case 54a bypass exhaust passage 56 Second cylindrical case 56a Main exhaust passage 60 switching valve 64 HC adsorbent 66 holes 72 EGR tube 72b outlet

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/02 F01N 3/08 A 3/08 3/18 F 3/18 F02M 25/07 580A F02M 25 / 07 580 580D B01D 53/36 B (72) Inventor Tadashi Sato 1-4-1, Chuo, Wako-shi, Saitama Prefecture Honda R & D Co., Ltd. No. F-term in Honda R & D Co., Ltd. (reference) 3G062 ED01 ED09 GA02 GA22 3G090 AA01 BA08 CB22 DB01 DB02 EA01 EA02 EA06 3G091 AA11 AA17 AA28 AB03 AB10 BA15 BA39 CA13 CA26 FA01 H04 H08 AB01 HB03A01 HB03A01 HB03A25 CC28 CD01

Claims (2)

[Claims] 1. A branch pipe is connected via a flange to an exhaust pipe for discharging exhaust gas of an internal combustion engine to the outside of the engine, and a main exhaust passage and an HC adsorbent are connected to the branch pipe. A bypass exhaust passage for accommodating the exhaust gas, the exhaust pipe is selectively connected to the main exhaust passage and the bypass exhaust passage through a switching valve, and the bypass exhaust passage is connected to an upstream position of the catalyst device. In an exhaust gas purification device for an internal combustion engine, which recirculates unburned HC components in exhaust gas adsorbed by the HC adsorbent through a pipe to the upstream side of the catalyst device, an outlet of the recirculation pipe is provided on a flange of the branch pipe. An exhaust emission control device for an internal combustion engine, which is formed integrally. 2. The bypass passage is airtightly fixed to an opening formed in a flange of the branch pipe, and a hole is formed at a position in the vicinity thereof corresponding to the take-out port. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the exhaust gas purification device is connected to the bypass exhaust passage.