JP2002256862A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the early activation of a catalyst which is provided in an exhaust emission control device for an internal combustion engine composed so as to reflux an exhaust gas to an intake system. SOLUTION: There is provided an EGR piping 15 for refluxing the exhaust gas from the downstream side of the catalyst 10 to the intake system (4a, 4b). Thereby, the refluxed exhaust gas is passed once through the catalyst 10, and since the heat thereof is utilized for warming-up of the catalyst 10 to activate it promptly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine having a catalyst in an exhaust system and recirculating exhaust gas to an intake system.

[0002]

2. Description of the Related Art A conventional exhaust gas purifying apparatus for an internal combustion engine includes:
The exhaust gas is recirculated to the intake system to lower the combustion temperature and suppress the generation of NOx (see, for example, JP-A-5-133285).

Further, harmful emissions (HC, CO, NOx, etc.) in exhaust gas are purified by a catalyst installed in an exhaust system. When the catalyst is warmed by the exhaust gas and becomes active (high temperature state), it exhibits sufficient performance. Therefore, when the catalyst is in an inactive state (low temperature state), the catalyst temperature is quickly raised to quickly start the catalyst. It is desired to be active.

[0004]

However, in the conventional apparatus, since all exhaust gas to be recirculated to the intake system is taken out from the upstream side of the catalyst, the recirculated exhaust gas does not pass through the catalyst. However, there is a problem that the catalyst is not used for warming up the catalyst and the catalyst cannot be activated early.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is directed to an exhaust gas purifying apparatus for an internal combustion engine which is provided with a catalyst in an exhaust system and recirculates exhaust gas to an intake system. It is an object of the present invention to effectively utilize the catalyst for warming up the catalyst and to activate the catalyst early.

[0006]

According to the first aspect of the present invention, an exhaust gas for an internal combustion engine having a catalyst (10) in an exhaust system (9a, 9b) of the internal combustion engine (1) is provided. The purification device is characterized in that the exhaust system (9a, 9b) is provided with an EGR passage (15) for recirculating exhaust gas from the downstream side of the catalyst (10) to the intake system (4a, 4b) of the internal combustion engine (1). And

According to this, since the exhaust gas is recirculated from the downstream side of the catalyst, the recirculated exhaust gas once passes through the catalyst. Therefore, the heat of the recirculated exhaust gas is used for warming up the catalyst, and the catalyst is quickly cooled. Can be activated.

According to the second aspect of the present invention, the catalyst (10) disposed in the exhaust system (9a, 9b) of the internal combustion engine (1).
A first EGR passage (14) for recirculating exhaust gas from an upstream side of the catalyst (10) in the exhaust system (9a, 9b) to the intake system (4a, 4b) of the internal combustion engine (1). In the exhaust gas purifying apparatus, the exhaust system (9a,
In 9b), the second EGR passage (15) for recirculating exhaust gas from the downstream side of the catalyst (10) to the intake system (4a, 4b) and the amount of exhaust gas recirculated to the intake system (4a, 4b) are controlled. The EGR valves (17, 18, 19) to be activated and the EGR valve (1
And control means (20) for controlling the EGR valves (17, 18, 1) by the control means (20).
9), the exhaust gas is recirculated through the first EGR passage (14) when the catalyst (10) is in an active state, and the second EGR is discharged when the catalyst (10) is in an inactive state.
The exhaust gas is recirculated through the passage (15).

According to this, when the catalyst is in an inactive state, the recirculated exhaust gas is taken in from the downstream side of the catalyst, so that the catalyst can be activated early as in the first aspect of the present invention. it can.

Further, since the state (composition, temperature, etc.) of the exhaust gas changes when the operating conditions of the internal combustion engine change, the path from the discharge of the exhaust gas to the recirculation of the exhaust gas to the intake system is made as short as possible. It is desirable to recirculate the latest exhaust gas. In the second aspect of the present invention, when the catalyst is in the active state, the exhaust gas is recirculated through the first EGR passage having a short path, so that the latest exhaust gas can be recirculated.

A second EGR valve (18) for adjusting the passage area downstream of the catalyst (10) in the exhaust system (9a, 9b), and a second EGR valve.
A third EGR valve (19) for opening and closing the GR passage (15) is provided, and when the catalyst (10) is in an inactive state, the second EG
The R valve (18) reduces the passage area of the exhaust system (9a, 9b), and the third EGR valve (19) fully opens the second EGR passage (15) to keep the catalyst (10) inactive. At some point, the exhaust gas can be recirculated through the second EGR passage (15).

The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the concrete means described in the embodiments described later.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 showing one embodiment of the present invention, reference numeral 1 denotes a diesel engine for driving a vehicle (hereinafter, referred to as a diesel engine).
The fuel is pressurized by a pump 2 driven by the internal combustion engine 1, and the pressurized fuel is injected from a fuel injection valve 3 into a combustion chamber of the internal combustion engine 1.

The intake system of the internal combustion engine 1 includes an intake pipe 4a and an intake manifold 4b. The intake pipe 4a is provided with a turbocharger for supercharging the air taken into the internal combustion engine 1 (hereinafter, this air is referred to as intake). A supercharger 5 of the type is provided. An air flow meter 6 for measuring the amount of intake air is provided upstream of the supercharger 5 in the intake pipe 4a and downstream of the supercharger 5 in the intake pipe 4a. , An intercooler 7 for cooling the intake air, and a throttle valve 8 for adjusting the intake air amount in conjunction with the accelerator pedal. Note that the throttle valve 8 includes an opening sensor for detecting the opening thereof, and the opening signal of the opening sensor corresponds to the depression amount signal of the accelerator pedal.

The exhaust system of the internal combustion engine 1 includes an exhaust pipe 9a and an exhaust manifold 9b, and two catalysts 10, 1 are disposed downstream of the supercharger 5 in the exhaust gas flow of the exhaust pipe 9a.
1 is provided.

The first catalyst 10, which is disposed upstream of the exhaust gas flow, of the catalysts 10, 11
It is an oxidation catalyst that purifies exhaust gas by accelerating the oxidation reaction of C and CO, and also has a function of collecting fine particles such as carbon contained in the exhaust gas. In the vicinity of the exhaust gas inlet of the first catalyst 10, the first catalyst 1
A first exhaust gas temperature sensor 12 for detecting the temperature of the exhaust gas flowing into the first catalyst 10 is provided. Near the exhaust gas outlet of the first catalyst 10, a first exhaust gas temperature sensor 12 for detecting the temperature of the exhaust gas after passing through the first catalyst 10 is provided. Two exhaust temperature sensors 13 are provided.

The second catalyst 11, which is disposed downstream of the first catalyst 10 in the exhaust gas flow, promotes the oxidation reaction of HC and CO in the exhaust gas to purify the exhaust gas. It is.

The intake pipe 4a and the exhaust manifold 9b are communicated with each other by a first EGR pipe (corresponding to an EGR passage) 14, and the first EGR pipe 14 recirculates exhaust gas taken in from the exhaust manifold 9b to the intake pipe 4a. Has become. Further, a second EGR pipe (corresponding to an EGR passage) 15 branched from between the first catalyst 10 and the second catalyst 11 in the exhaust pipe 9a is connected to the first EGR pipe 14, and the exhaust gas flow downstream of the first catalyst 10 The exhaust gas taken in from the side is introduced into the intake pipe 4 via the first EGR pipe 14.
a. Here, the first EGR
From the exhaust manifold 9 b in the pipe 14 to the second EGR
The passage area of the second EGR pipe 15 is made larger than the passage area to the connection portion of the pipe 15 so that the pressure loss of the second EGR pipe 15 is relatively reduced.

An EGR cooler 16 for cooling the exhaust gas taken in from the exhaust manifold 9b is provided between the exhaust manifold 9b in the first EGR pipe 14 and a connecting portion of the second EGR pipe 15. Also,
In the first EGR pipe 14, between the connection portion of the second EGR pipe 15 and the intake pipe 4a, a first EGR valve 17 for controlling the amount of exhaust gas recirculated to the intake pipe 4a is provided.

In the exhaust pipe 9a, the second EGR pipe 15
A second EGR valve that adjusts a passage area in the exhaust pipe 9a downstream of the connecting portion of the exhaust gas and the installation position of the second exhaust gas temperature sensor 13 and upstream of the exhaust gas flow of the second catalyst 11. 18 are provided. Also, the second EGR
In a portion of the pipe 15 near the exhaust pipe 9a, the second EG
A third EGR valve 19 for adjusting a passage area in the R pipe 15 is provided.

An electronic control unit 2 for controlling the operations of the pump 2, the fuel injection valve 3, and the first to third EGR valves 17 to 19
0 (hereinafter referred to as ECU)
, An opening signal from the throttle valve 8, a temperature signal from both exhaust temperature sensors 12, 13, and a temperature signal from a water temperature sensor 21 for detecting the temperature of the cooling water of the internal combustion engine 1. Further, signals such as the rotation speed of the internal combustion engine 1 and the pressure in the intake pipe 4a are also input.

The ECU 20 determines the fuel injection amount, the fuel injection timing, the fuel injection timing based on the rotation speed of the internal combustion engine 1 and the opening degree of the throttle valve 8 (ie, the depression amount of the accelerator pedal) among the above signals. The injection pressure and the like are calculated, and the operations of the pump 2 and the fuel injection valve 3 are controlled so that the calculated fuel injection amount and the like are realized. Further, the ECU 20 determines whether the first catalyst 10 is in an active state, and controls the first to third EGR valves 17 to 19 based on the determination result.

In the above configuration, when the internal combustion engine 1 is started, the ECU 20 determines whether the first catalyst 10 is in an active state. Specifically, based on the fact that the temperature of the first catalyst 10 and the cooling water temperature of the internal combustion engine 1 are substantially proportional, when the cooling water temperature of the internal combustion engine 1 detected by the water temperature sensor 21 is equal to or lower than a predetermined temperature, Determines that the first catalyst 10 is in an inactive state (low temperature state), and when the cooling water temperature of the internal combustion engine 1 exceeds a predetermined temperature, the first catalyst 10 is in an active state (high temperature state).
Is determined. Here, the predetermined temperature is desirably set to a value higher than the outside air temperature, for example, 50 to 60 ° C.

When the internal combustion engine 1 has been stopped for a long time, the cooling water temperature is substantially equal to the outside air temperature.
When the internal combustion engine 1 is started after such a long stop, the ECU 20 determines that the first catalyst 10 is in the inactive state because the cooling water temperature is equal to or lower than the predetermined temperature.

When it is determined that the first catalyst 10 is in the inactive state, the exhaust gas taken in from the downstream side of the first catalyst 10 is supplied from the second EGR pipe 15 to the first EGR pipe 1
The ECU 20 is configured to return to the intake pipe 4a through the ECU 4.
Controls the opening degrees of the first to third EGR valves 17 to 19.

More specifically, the second EGR valve 18 is set to an almost full-closed position and the third EGR valve 19 is fully opened to facilitate the flow of the exhaust gas to the second EGR pipe 15. Further, as the fuel injection amount decreases, the intake pipe 4
a so as to increase the amount of recirculation of exhaust gas to the first EGR.
The opening of the valve 17 and the second EGR valve 18 is controlled.

Although a small amount of the exhaust gas taken in from the exhaust manifold 9b is recirculated, the second EGR pipe 1
Since the passage area of the passage 5 is increased to reduce the pressure loss, the exhaust gas taken in from the downstream side of the first catalyst 10 is mainly recirculated.

As described above, when it is determined that the first catalyst 10 is in the inactive state, the exhaust gas taken in from the downstream side of the first catalyst 10 is recirculated so that the first catalyst 1
0 can be activated early.

That is, in the conventional device, the intake pipe 4
Since all exhaust gas refluxed to a is taken out from the upstream side of the first catalyst 10, the reflux exhaust gas does not pass through the first catalyst 10, so that heat of the reflux exhaust gas is not used for warming up the first catalyst 10. .

On the other hand, in the present embodiment, the first catalyst 1
0 through the second EGR pipe 15 from the downstream side of the intake pipe 4a.
Since the exhaust gas that is recirculated to the first catalyst once passes through the first catalyst 10, the heat of the recirculated exhaust gas is used for warming up the first catalyst 10.
Can be activated early.

When the first catalyst 10 is activated, the oxidation of HC and CO in the exhaust gas is promoted by the first catalyst 10, and the exhaust gas is purified.

Next, when the cooling water temperature rises with the operation of the internal combustion engine 1 and the cooling water temperature exceeds a predetermined temperature, the ECU 20
Determines that the first catalyst 10 is in the active state.

As described above, when it is determined that the first catalyst 10 is in the active state, the second EGR valve 18 is fully opened, the third EGR valve 19 is fully closed, and the exhaust gas extracted from the exhaust manifold 9b is exhausted. Only the first EGR pipe 14
To the intake pipe 4a. At this time, as in the conventional case, the first EGR valve 17 is controlled so that the amount of recirculated exhaust gas to the intake pipe 4a increases as the fuel injection amount decreases.
Control the opening degree.

After the first catalyst 10 has been activated, the temperature of the second catalyst 11 gradually increases with time, and when the second catalyst 11 is activated, the two catalysts 10 and 11 are activated.
The exhaust gas is thus purified.

When the operating conditions of the internal combustion engine 1 change, the state (composition, temperature, etc.) of the exhaust gas changes, so that the path from the discharge of the exhaust gas to the recirculation to the intake pipe 4a should be as small as possible. It is desirable to keep it short and to recycle the latest exhaust gas. And the exhaust manifold 9b
Is shorter than the path from the exhaust manifold 9b to the intake pipe 4a via the first catalyst 10 and the second EGR pipe 15 because the path for returning to the intake pipe 4a via the first EGR pipe 14 is shorter than the former. The recirculation through the path of (1) allows the latest exhaust gas to be recirculated earlier. In the present embodiment, in consideration of the above points, the first catalyst 1
After 0 becomes active, the exhaust gas is recirculated only through the first EGR pipe 14.

(Other Embodiments) In the above embodiment, whether or not the first catalyst 10 is in the active state is determined based on the cooling water temperature of the internal combustion engine 1. However, the present start is performed after the internal combustion engine 1 is stopped. The determination may be made based on the elapsed time until the determination is made. That is, the longer the stop time of the internal combustion engine 1, the lower the temperature of the first catalyst 10. Therefore, when the elapsed time from the stop of the internal combustion engine 1 to the present start is longer than a predetermined time (for example, 20 minutes), It may be determined that one catalyst 10 is in an inactive state.

When the first catalyst 10 is in the inactive state, the exhaust gas absorbs heat when passing through the first catalyst 10 and the temperature of the exhaust gas decreases. On the other hand, when the first catalyst 10 is in the active state, If present, HC in the exhaust gas by the first catalyst 10,
The oxidation of CO is promoted and the temperature of the exhaust gas rises. Therefore, the exhaust gas temperature sensors 12 provided before and after the first catalyst 10,
13 (see FIG. 1), the temperature of the exhaust gas flowing into the first catalyst 10 and the temperature of the exhaust gas after passing through the first catalyst 10 are detected, and the temperature of the exhaust gas flowing into the first catalyst 10 is set to the first temperature.
When the temperature of the exhaust gas after passing through the catalyst 10 is lower, the first
It may be determined that the catalyst 10 is in an inactive state.

In the above embodiment, the first EGR
The fourth E pipe is located on the exhaust gas flow upstream side (exhaust manifold 9b side) of the connection portion of the second EGR pipe 15 in the pipe 14.
A GR valve may be provided. When it is determined that the first catalyst 10 is in the inactive state, the fourth EGR valve is closed to stop the intake of the exhaust gas from the exhaust manifold 9b, and the exhaust gas returning to the intake pipe 4a is completely discharged. First
It is taken in from the downstream side of the catalyst 10. According to this, when it is determined that the first catalyst 10 is in the inactive state, all of the exhaust gas recirculated to the intake pipe 4a is temporarily discharged to the first
Since the first catalyst 10 passes through the catalyst 10, the temperature rise of the first catalyst 10 can be further accelerated.

In the above-described embodiment, the second EGR pipe 15 is connected between the EGR cooler 16 and the first EGR valve 17 in the first EGR pipe 14, but the exhaust gas flow upstream of the EGR cooler 16. The second EGR pipe 15 may be connected.

In the above embodiment, the second EGR
By branching the pipe 15 from the downstream side of the second catalyst 11 and circulating the exhaust gas taken in from the downstream side of the second catalyst 11, both the first catalyst 10 and the second catalyst 11 can be activated early. it can.

In the above embodiment, both catalysts 10, 11
Although the co-oxidation catalyst is used, both the catalysts 10 and 11 may be a three-way catalyst, or one of the two catalysts 10 and 11 may be an oxidation catalyst and the other may be a three-way catalyst. Further, both catalysts 10, 11 or one of both catalysts 10, 11
An oxidation catalyst having a function of collecting fine particles such as carbon contained in exhaust gas may be used. .

In the above embodiment, two catalysts 10,
Although 11 is used, the second catalyst 11 may be omitted.

The present invention can be applied not only to the diesel engine described above but also to a gasoline engine.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an exhaust gas purifying apparatus for an internal combustion engine according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 4a, 4b ... Intake system, 9a, 9b ... Exhaust system, 10 ... Catalyst, 15 ... EGR piping.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F02D 21/08 F02M 25/07 570J F02M 25/07 550 580A 570 580G 580 B01D 53/36 ZABB 103C (72) Inventor Kuboshima Tsukasa 1-chome, Showa-cho, Kariya-shi, Aichi Prefecture In-house Denso Corporation (72) Inventor Tatsuya Fujita 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture F-term in Denso Corporation 3G062 AA01 AA03 AA05 AA06 BA02 BA04 BA05 BA06 CA01 CA02 CA03 CA06 CA07 CA10 DA01 DA02 EA10 EB04 EB15 ED01 ED08 ED10 ED11 ED12 FA24 GA01 GA02 GA04 GA06 GA08 GA09 GA14 GA17 3G091 AA02 AA10 AA11 AA17 AA18 AA28 AB02 AB03 AB13 BA03 BA03 CB02 EA05 EA06 EA07 EA16 EA17 EA26 EA30 FA02 FA04 FA06 FB02 FB03 FB10 FC04 FC07 HA08 HA14 HA36 HA37 HA42 HB03 HB05 3G092 AA01 AA02 AA06 AA13 AA17 AA18 AB02 AB03 BA01 BA04 BB01 DB08 DC09 DC10 DC12 DC02 EA11 EA12 EA21 EA22 EA28 EA29 4D048 AA13 AA18 AB01 BD01 CC27 CC32 CC41 CC44 CC53 DA01 DA02 DA05 DA06

Claims (3)

[Claims] An exhaust system (9a, 9b) for an internal combustion engine (1).
An exhaust gas purifying apparatus for an internal combustion engine, further comprising a catalyst (10), wherein the exhaust system (9a, 9b) has an intake system (4a, 4a, 4b) of the internal combustion engine (1) from a downstream side of the catalyst (10).
An exhaust gas purifying apparatus for an internal combustion engine, comprising an EGR passage (15) for recirculating exhaust gas in b). 2. An exhaust system (9a, 9b) of an internal combustion engine (1).
Catalyst (10) disposed in the exhaust system (9a, 9b)
And a first EGR passage (14) for recirculating exhaust gas from an upstream side of the catalyst (10) to an intake system (4a, 4b) of the internal combustion engine (1). A second EGR passage (15) for recirculating exhaust gas to the intake system (4a, 4b) from a downstream side of the catalyst (10) in the exhaust system (9a, 9b); and a recirculation to the intake system (4a, 4b). EGR valves (17, 18, 19) for controlling the amount of exhaust gas to be discharged, and the EG based on whether the catalyst (10) is in an active state or not.
Control means (20) for controlling the R valves (17, 18, 19)
The EGR valve (17, 1) is controlled by the control means (20).
8, 19) to recirculate the exhaust gas through the first EGR passage (14) when the catalyst (10) is in an active state, and to control the exhaust gas recirculation through the first EGR passage (14) when the catalyst (10) is in an inactive state. Is an exhaust gas purifying apparatus for an internal combustion engine, wherein exhaust gas is recirculated through the second EGR passage (15). 3. The EGR valve (17, 18, 19)
A second EGR valve (18) for adjusting a passage area downstream of the catalyst (10) in the exhaust system (9a, 9b);
A third EGR for opening and closing the second EGR passage (15)
A valve (19), wherein when the catalyst (10) is in an inactive state, the second E
The GR valve (18) makes the passage area of the exhaust system (9a, 9b) smaller than when the catalyst (10) is in an active state, and the third EGR valve (19) makes the second EGR
The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein the passage (15) is fully opened.