JPH09100714A - Exhaust emission control system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a failure caused by exhaust gas leaked from an exhaust change-over valve. SOLUTION: An exhaust emission control system is provided with a first EGR passage 11 for connecting a catalyst passage in an upstream side more than an upstream catalyst converter 2 more than an exhaust change-over valve 4 with an air intake passage 8, a second EGR passage 12 for connecting a bypass passage 10 with the air intake passage 8, an EGR passage change-over valve 7 for selectively opening the first and second EGR passages 11 and 12 and a control unit 5 for actuating the EGR passage change-over valve 7 so as to re-circulate exhaust gas leaked from the exhaust change-over valve 4 to the air intake passage 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In an automobile internal combustion engine or the like, in order to purify exhaust gas, feedback control is performed so that an air-fuel ratio becomes a stoichiometric air-fuel ratio, and HC and CO are oxidized and NOx is reduced in an exhaust passage. A system equipped with a three-way catalyst that simultaneously performs the above is widely put into practical use.

In order to accelerate the activation of the catalyst at a low temperature, there is one in which a catalytic converter is installed immediately below the exhaust manifold of the engine.

In order to ensure the heat resistance of the upstream catalytic converter installed directly below the exhaust manifold, there are some which are equipped with an exhaust switching valve that restricts the introduction of exhaust gas into the upstream catalytic converter during operation where the exhaust gas becomes hot ( See Japanese Laid-Open Patent Publication No. 57-210116).

[0005]

However, even when the exhaust gas switching valve closes the upstream catalytic converter, exhaust gas leaking through the gap around the exhaust gas switching valve is guided to the upstream catalytic converter, which causes deterioration of the catalyst. The problem of speeding up is considered.

Further, even when the bypass passage bypassing the upstream catalytic converter by the exhaust gas switching valve is closed, the exhaust gas leaking from the gap around the exhaust gas switching valve bypasses the upstream catalytic converter and is discharged without being purified. However, there is a problem that the exhaust emission is deteriorated.

An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine, which solves the above-mentioned problems caused by exhaust gas leaking from the exhaust gas switching valve.

[0008]

An exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein an exhaust gas purification catalytic converter is installed in the exhaust passage, and a bypass passage for bypassing the catalytic converter to guide the exhaust gas. Exhaust passage switching means for restricting introduction of exhaust gas into the catalytic converter or the bypass passage according to operating conditions, and first EGR connecting the exhaust passage downstream of the exhaust passage switching means and upstream of the catalytic converter to the intake passage
The passage, the second EGR passage connecting the intake passage and the bypass passage downstream of the exhaust passage switching means, and the first EG for recirculating the exhaust gas leaking from the exhaust passage switching means to the intake passage.
EGR passage switching means for selectively opening the R passage and the second EGR passage.

The exhaust gas purifying apparatus for an internal combustion engine according to a second aspect is the exhaust gas purifying apparatus according to the first aspect, wherein the EGR passage switching means selectively opens the first EGR passage and the second EGR passage. A switching valve, control means for operating the EGR passage switching valve to open the first EGR passage during operation in which introduction of exhaust gas to the catalytic converter is limited, and during operation in which introduction of exhaust gas to the bypass passage is restricted. Control means for operating the EGR passage switching valve so as to open the second EGR passage.

According to a third aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to the first or second aspect of the invention, a guide rib that guides the exhaust gas leaking from the exhaust passage switching means to the first EGR passage or the second EGR passage. Equipped with.

An exhaust gas purifying apparatus for an internal combustion engine according to a fourth aspect is the exhaust gas purifying apparatus according to any one of the first to third aspects, in which a portion of the exhaust passage to which the first EGR passage or the second EGR passage is connected is connected. A throttle for reducing the flow passage area on the downstream side is provided.

[0012]

In the exhaust gas purifying apparatus for an internal combustion engine according to claim 1, the exhaust gas leaking from the exhaust passage switching means is recirculated to the intake passage through the second EGR passage when the bypass passage is closed. As a result, it is possible to prevent the leaked exhaust gas from being discharged to the outside without being purified, and prevent the exhaust emission from deteriorating.

In the operating state in which the flow path of the catalytic converter is blocked, the exhaust gas leaking from the exhaust passage switching means is the first EGR.
By recirculating through the passage to the intake passage, high-temperature leaked exhaust gas can be prevented from being guided to the catalytic converter and deterioration of the catalytic converter.

In the exhaust gas purifying apparatus for an internal combustion engine according to a second aspect, the EG is operated when the bypass passage is closed.
The second EGR passage is opened via the R passage switching valve.
As a result, the exhaust gas leaking from the exhaust passage switching means is recirculated to the intake passage through the second EGR passage, and it is possible to prevent the leaked exhaust gas from being discharged to the outside without being purified, and prevent the deterioration of exhaust emission. it can.

In the operating state in which the flow path of the catalytic converter is closed, the first EGR passage is opened via the EGR passage switching valve. As a result, the exhaust gas leaking from the exhaust passage switching means is recirculated to the intake passage through the first EGR passage, so that high-temperature leaked exhaust gas is guided to the catalytic converter and deterioration of the catalytic converter is suppressed. To be

In the exhaust gas purifying apparatus for an internal combustion engine according to claim 3, the exhaust gas leaking from the exhaust passage switching means is guided by the guide ribs to be guided to the first EGR passage or the second EGR passage, and is re-introduced to the intake passage. It is encouraged to circulate.

In the exhaust gas purifying apparatus for an internal combustion engine according to claim 4, the flow of the exhaust gas leaking from the exhaust passage switching means is
The resistance is applied through the diaphragm, so that the first EGR
It is guided to the passage or the second EGR passage and is urged to recirculate to the intake passage.

[0018]

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

As shown in FIG. 1, an upstream catalytic converter 2 and a downstream catalytic converter 3 are installed in series in an exhaust passage 9 of an engine 1 to oxidize HC and CO in exhaust gas and NOx.
Are reduced at the same time.

A fuel injection valve (not shown) is attached to the intake passage 8 of the engine 1, and fuel is injected in response to a signal from the control unit 5.

Although not shown, the control unit 5 inputs detection signals such as the engine intake air amount Q and the rotation speed N to make the air-fuel ratio close to the theoretical air-fuel ratio T.
When p (= K × Q / N; K is a constant) is calculated, the detection signal of the O ₂ sensor is input so that the fuel injection amount falls within a narrow range around the target value in a predetermined stoichiometric range. Then, the final fuel injection amount Ti is calculated by the following equation and the air-fuel ratio is feedback-controlled.

Ti = Tp × α × COEF + Ts (1) where α is the air-fuel ratio feedback correction coefficient, COEF
Is the sum of various correction coefficients with the engine cooling water temperature as a parameter, and Ts is the invalid injection pulse width.

The upstream catalytic converter 2 is arranged as close to the engine 1 as possible so as to accelerate the activation at a low temperature of the catalyst.

In the exhaust passage 9, exhaust gas from the engine 1 bypasses the upstream catalytic converter 2 and the downstream catalytic converter 3
A bypass passage 10 that leads to is provided.

As an exhaust passage switching means for restricting the introduction of the exhaust gas into the upstream catalytic converter 2 or the bypass passage 10 in accordance with the operating conditions, the exhaust passage 9 is an exhaust passage for selectively opening the bypass passage 10 and the upstream catalytic converter 2. The switching valve 4 is interposed.

The control unit 5 uses the exhaust passage switching valve 4 to bypass the bypass passage 10 when the exhaust temperature is low.
Is closed to guide the exhaust gas to the upstream catalytic converter 2, purify the exhaust gas via the upstream catalytic converter 2, and accelerate the activation of the downstream catalytic converter 3.

By the way, even in the operating state in which the exhaust passage valve 4 bypasses the upstream catalytic converter 2 and the bypass passage 10 is closed, the exhaust gas leaking from the gap or the like around the exhaust passage valve 4 is guided to the bypass passage 10. If the leaked exhaust gas flowing through the bypass passage 10 is discharged to the outside through the inactive downstream catalytic converter 3, the exhaust emission is deteriorated.

Further, the exhaust switching valve 4 is provided in the bypass passage 1
Even in an operating state in which 0 is opened and the upstream catalytic converter 2 is closed, exhaust gas leaking from a gap or the like around the exhaust gas switching valve 4 is guided to the upstream catalytic converter 2. When the high-temperature leaked exhaust flowing toward the upstream catalytic converter 2 is guided to the upstream catalytic converter 2, the upstream catalytic converter 2
Accelerate the deterioration of.

In response to this, the present invention, the first EGR passage 11 connecting the exhaust passage 9 and the intake passage 8 on the downstream side of the exhaust switching valve 4 and on the upstream side of the catalytic converter 2, the bypass passage 10 and the intake passage 8 are connected. Second EGR passages 12 connecting the two are respectively arranged, and the first EGR passage 11 and the second EGR passage 1 are connected.
EGR passage switching means for selectively opening 2 to recirculate the exhaust gas leaking from the exhaust switching valve 4 to the intake passage 8 is provided.

As an EGR passage switching means, an EGR passage switching valve 7 is provided at a branch portion between the first EGR passage 11 and the second EGR passage 12. The EGR passage switching valve 7 is
It has a position where the first EGR passage 11 is opened and the second EGR passage 12 is closed, and a position where the first EGR passage 11 is closed and the second EGR passage 12 is opened.

The control unit 5 switches the position of the EGR passage switching valve 7 so that the EGR gas is taken in from the passage where the introduction of the exhaust gas is restricted via the exhaust switching valve 4. That is, the first EGR passage 11 is opened during the operation in which the introduction of the exhaust gas into the upstream catalytic converter 2 via the exhaust switching valve 4 is restricted, while the introduction of the exhaust gas into the bypass passage 10 via the exhaust switching valve 4 is prevented. The second EGR passage 12 is opened during the limited operation.

An EGR valve 6 is provided at the confluence of the first EGR passage 11 and the second EGR passage 12 connecting the EGR passage switching valve 7 and the intake passage 8. The control unit 5 controls the opening degree of the EGR valve 6 according to the operating condition of the engine 1, and the amount of EGR gas recirculated from the exhaust passage 9 to the intake passage 8 is adjusted. As a result, inactive E in the intake passage 8
The GR gas is recirculated to suppress the generation of NOx.

FIG. 2 shows a routine for controlling the operations of the exhaust switching valve 4, the EGR passage switching valve 7 and the EGR valve 6, respectively.

Explaining this, first, at step 1, the exhaust temperature Tmp is calculated according to the engine speed N and the basic fuel injection amount Tp based on the map shown in FIG. The exhaust temperature Tmp is set to a larger value as the basic fuel injection amount Tp increases and the engine speed N increases.

Subsequently, at step 2, the exhaust gas temperature Tmp accelerates the deterioration of the upstream catalytic converter 2 by a predetermined value TR (for example, 7).
00 ° C) or less is determined.

When the exhaust temperature Tmp is determined to be equal to or lower than the predetermined value TR, the routine proceeds to step 3, where the exhaust switching valve 4 is opened to guide the exhaust to the upstream catalytic converter 2. At this time, the bypass passage 10 is closed by the exhaust switching valve 4.

In this way, the exhaust gas is purified by both the upstream catalytic converter 2 and the downstream catalytic converter 3 at a low exhaust temperature when the downstream catalytic converter 3 is not sufficiently activated, and the deterioration of the exhaust emission is suppressed. At EG
The R passage switching valve 7 is switched to a position where the second EGR passage 12 is opened and the first EGR passage 11 is closed.

In this way, the leaked exhaust gas flowing through the bypass passage 10 passes through the second EGR passage 12 and the intake passage 8
By recirculating the exhaust gas to the outside, it is possible to prevent the leaked exhaust gas from being discharged to the outside through the inactive downstream catalytic converter 3 without being purified, and it is possible to prevent deterioration of the exhaust emission.

In step 5, the drive amount Es of the EGR valve 6 is calculated according to the engine speed N and the basic fuel injection amount Tp based on the map shown in FIG. 4, and the EGR valve 6 is driven.

When it is determined that the exhaust gas temperature Tmp is higher than the predetermined value TR, the routine proceeds to step 6, where the exhaust gas switching valve 4 closes the catalyst passage 20 and the exhaust gas bypasses the upstream catalytic converter 2 through the bypass passage 10. To the downstream catalytic converter 3.

In this way, when the downstream catalytic converter 3 is sufficiently activated and the exhaust gas temperature is high, the exhaust gas is purified only by the downstream catalytic converter 3 and the deterioration of the upstream catalytic converter 2 is suppressed.

Subsequently, in step 7, the first EGR passage 11 opens the EGR passage switching valve 7 and the second EGR passage 1 is opened.
Switch to the position where 2 is closed.

In this way, the leaked exhaust gas flowing toward the upstream catalytic converter 2 is recirculated to the intake passage 8 through the first EGR passage 11, whereby the high temperature leaked exhaust gas is guided to the upstream catalytic converter 2. As a result, the deterioration of the upstream catalytic converter 2 can be suppressed.

Subsequently, at step 8, the drive amount Es of the EGR valve 6 is calculated according to the engine speed N and the basic fuel injection amount Tp based on the map shown in FIG. 5, and the EGR valve 6 is driven.

Next, another embodiment shown in FIG. 6 will be described. 1 and the like parts are designated by the same reference numerals.

The tubular exhaust passage 9 is partitioned by a partition wall 21 into a bypass passage 10 and a catalyst passage 20 in which the upstream catalytic converter 2 is interposed. The bypass passage 10 and the catalyst passage 20 have a semi-elliptical cross section.

As shown also in FIG. 8, the valve body 25 of the exhaust switching valve 4 is formed in a semi-elliptical shape, and is rotated by an actuator (not shown) via the rotary shaft 22. The rotating shaft 22 is provided along the upstream end of the partition wall 21.

The exhaust gas switching valve 4 opens the catalyst passage 20 and closes the bypass passage 10 at the position shown, and rotates 180 ° from this position as shown by the arrow in FIG. 7 to open the catalyst passage 20. It is switched to a position where it is closed and the bypass passage 10 is opened.

Even when the exhaust switching valve 4 is in the position where it blocks the bypass passage 10, there is a gap 19 around the valve body 25 of the exhaust switching valve 4.

The bypass passage 10 includes a second EGR passage 12
A guide rib 23 is provided on the upstream side of the inlet. The guide rib 23 is attached so as to be inclined toward the entrance of the second EGR passage 12.

The exhaust gas leaking from the gap 19 of the exhaust gas switching valve 4 is guided to the second EGR passage 12 by being guided by the guide rib 23 as shown by the arrow in FIG. It is encouraged to recycle to 8.

Further, the bypass passage 10 has a throttle 2 for reducing the flow passage area downstream from the inlet of the second EGR passage 12.
4 are provided.

The flow of the leaked exhaust gas flowing through the bypass passage 10 is suppressed from flowing to the downstream side of the exhaust passage 9 due to the resistance imparted through the throttle 24, so that the second EGR is performed.
Recirculation through the passage 12 to the intake passage 8 is encouraged.

In this way, the intake passage 8 passes through the second EGR passage 12 via the guide rib 23 and the throttle 24.
By promoting the recirculation of the exhaust gas to the outside, it is possible to prevent the leaked exhaust gas from being discharged to the outside through the inactive downstream catalytic converter 3 without being purified, and it is possible to prevent deterioration of the exhaust emission.

Next, another embodiment shown in FIG. 9 will be described. 1 and the like parts are designated by the same reference numerals.

In the exhaust passage 9, a bypass passage 10 and a catalyst passage 20 in which the upstream catalytic converter 2 is interposed are defined in a tubular shape. The bypass passage 10 and the catalyst passage 20 have a substantially circular cross section.

As shown in FIG. 9, the exhaust switching valve 4
Has a valve body 26 that opens and closes the catalyst passage 20 and a valve body 27 that opens and closes the bypass passage 10, and the valve bodies 26 and 27 are rotatably provided via a common rotation shaft 28. The valve bodies 26 and 27 are rotated by a not-shown actuator via a rotary shaft 28.

The disc-shaped valve bodies 26 and 27 are separated from each other by 9
It is fixed to the rotary shaft 28 with a phase difference of 0 °. As a result, the exhaust gas switching valve 4 opens the bypass passage 10 when the valve body 26 closes the catalyst passage 20, and closes the bypass passage 10 when the valve body 26 opens the catalyst passage 20.

The exhaust gas switching valve 4 opens the catalyst passage 20 at the illustrated position and closes the bypass passage 10 and rotates 90 ° from this position as shown by the arrow in FIG. 10 to open the catalyst passage 20. It is switched to a position where it is closed and the bypass passage 10 is opened.

Even when the exhaust gas switching valve 4 is in the position where it closes the bypass passage 10, there is a gap 29 around the valve body 27 of the exhaust gas switching valve 4.

The second EGR passage 12 is provided in the bypass passage 10.
A guide rib 33 is provided on the upstream side of the inlet of the. The guide rib 33 is attached so as to be inclined toward the inlet of the second EGR passage 12.

The exhaust gas leaking from the gap 19 of the exhaust gas switching valve 4 is guided to the second EGR passage 12 by being guided by the guide rib 33 as shown by the arrow in FIG. It is encouraged to recycle to 8.

Further, the bypass passage 10 is provided with a throttle 34 for narrowing the passage downstream from the inlet of the second EGR passage 12.

The flow of the leaked exhaust gas flowing through the bypass passage 10 is suppressed from flowing to the downstream side of the exhaust passage 9 due to the resistance imparted through the throttle 34, so that the second EGR is performed.
Recirculation through the passage 12 to the intake passage 8 is encouraged.

In this way, the intake passage 8 passes through the second EGR passage 12 via the guide rib 33 and the throttle 34.
By promoting the recirculation of the exhaust gas to the outside, it is possible to prevent the leaked exhaust gas from being discharged to the outside through the inactive downstream catalytic converter 3 without being purified, and it is possible to prevent deterioration of the exhaust emission.

[0066]

As described above, the exhaust gas purifying apparatus for the internal combustion engine according to claim 1 has the first EGR passage and the second EGR.
By selectively opening the passage and recirculating the exhaust gas leaking from the exhaust passage switching means to the intake passage, it is possible to prevent the leaked exhaust gas from being discharged to the outside without being purified,
Exhaust emissions can be prevented from deteriorating, and high-temperature leaked exhaust gas can be prevented from being guided to the catalytic converter and deterioration of the catalytic converter.

According to a second aspect of the present invention, there is provided an exhaust gas purifying apparatus for an internal combustion engine, wherein the first EGR passage and the second EGR passage are selectively opened via an EGR passage switching valve so that the exhaust gas leaked from the exhaust passage switching means is taken in. By recirculating the exhaust gas to the outside, the leaked exhaust gas is suppressed from being discharged to the outside without being purified, deterioration of exhaust emission is suppressed, and high-temperature leaked exhaust gas is guided to the catalytic converter to deteriorate the catalytic converter. Can be suppressed.

In the exhaust gas purifying apparatus for an internal combustion engine according to a third aspect, the exhaust gas leaking from the exhaust passage switching means is guided by the guide ribs to the first EGR passage or the second EGR passage and is recirculated to the intake passage. Is promoted, the deterioration of the catalytic converter is suppressed, and the deterioration of exhaust emission is suppressed.

In the exhaust gas purifying apparatus for an internal combustion engine according to the fourth aspect, the flow of the exhaust gas leaked from the exhaust passage switching means is applied to the first EGR passage or the second EGR passage by applying resistance through the throttle. Then, recirculation in the intake passage is promoted, deterioration of the catalytic converter is prevented from progressing, and deterioration of exhaust emission is suppressed.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a flow chart showing control contents for operating each valve.

FIG. 3 is a map in which an exhaust temperature Tmp is also set based on operating conditions.

FIG. 4 is a map similarly setting the operation amount of the EGR valve.

FIG. 5 is a map similarly setting the operation amount of the EGR valve.

FIG. 6 is a perspective view of an intake system showing another embodiment.

FIG. 7 is a perspective view of an exhaust switching valve of the same.

FIG. 8 is a plan view of the exhaust switching valve which is also closed.

FIG. 9 is a perspective view of an intake system showing still another embodiment.

FIG. 10 is a perspective view of an exhaust switching valve of the same.

FIG. 11 is a plan view of the exhaust switching valve which is also closed.

[Explanation of symbols]

 1 engine 2 upstream catalytic converter 3 downstream catalytic converter 4 exhaust switching valve 5 control unit 6 EGR valve 7 EGR passage switching valve 8 intake passage 9 exhaust passage 10 bypass passage 11 first EGR passage 12 second EGR passage 23 guide rib 24 throttle 33 guide rib 34 Aperture

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Tsuchida 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (4)

[Claims] 1. A catalytic converter for purifying exhaust gas installed in an exhaust passage, a bypass passage for guiding exhaust gas bypassing the catalytic converter, and limiting introduction of exhaust gas into the catalytic converter or bypass passage according to operating conditions. An exhaust passage switching means, a first EGR passage connecting an exhaust passage downstream of the exhaust passage switching means and upstream of the catalytic converter with an intake passage, and a second EGR passage connecting a bypass passage downstream of the exhaust passage switching means with the intake passage An EGR passage, and EGR passage switching means for selectively opening the first EGR passage and the second EGR passage so that exhaust gas leaked from the exhaust passage switching means is recirculated to the intake passage. Exhaust gas purification device for internal combustion engine. 2. An EGR passage switching valve that selectively opens the first EGR passage and the second EGR passage as the EGR passage switching means, and a first EGR passage during operation in which introduction of exhaust gas to the catalytic converter is restricted. A control unit that operates the EGR passage switching valve to open the EGR passage switching valve, and a control unit that operates the EGR passage switching valve to open the second EGR passage during an operation in which introduction of exhaust gas into the bypass passage is restricted. The exhaust emission control device for an internal combustion engine according to claim 1, further comprising: 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, further comprising a guide rib for guiding the exhaust gas leaking from the exhaust gas passage switching means to the first EGR passage or the second EGR passage. 4. A first EGR passage or a second EG of an exhaust passage
The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 3, further comprising a throttle that reduces a flow passage area on a downstream side of a portion to which the R passage is connected.