JP2003020933A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent clogging of a DPF when providing the DPF for scavenging PM in exhaust in an exhaust passage of an engine. SOLUTION: In the case of a regeneration region (high load region) of the DPF (S3), PM accumulated amount W1 of the DPF is estimated from exhaust pressure Pexh on an upstream side of the DPF (S4). PM combustion amount V1 of the DPF is estimated from the PM accumulated amount W1 (S5). PM inflow amount V0 to flow into the DPF is estimated from the present excess air ratio λ0 (S6). The PM combustion amount V1 and the PM inflow amount V0 are compared (S7). In the case of V0>=V1, the excess air ratio is increased (S8).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a particulate filter (generally referred to as a diesel particulate filter, henceforth referred to as DPF) for collecting particulate matter (hereinafter referred to as PM) in exhaust gas in an exhaust passage of an engine. The present invention relates to an exhaust emission control device for an internal combustion engine.

[0002]

2. Description of the Related Art A DPF collects PM in exhaust gas and
The PM is removed by burning the PM in F. Whether PM burns in the DPF depends on the exhaust temperature, and burns only when the exhaust temperature is equal to or higher than a predetermined temperature. Therefore, when the exhaust temperature is lower than the predetermined temperature, the PM in the DPF increases without burning,
Since the DPF will be clogged, if the amount of PM trapped in the DPF (PM accumulation amount) exceeds a predetermined amount,
It is necessary to force playback.

As a technique for forcibly regenerating the DPF, for example, a technique disclosed in Japanese Patent Laid-Open No. 11-280449 is known.

[0004]

However, even when the PM in the DPF is burning at the exhaust temperature above the predetermined temperature, when the amount of PM discharged from the engine and flowing into the DPF is too large. That is, when the PM amount per unit time flowing into the DPF (PM inflow amount) exceeds the PM amount per unit time burning in the DPF (PM combustion amount), the PM accumulation amount in the DPF increases. However, as a result, there is a problem that clogging occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and an object thereof is to reliably prevent clogging of a DPF.

[0006]

For this reason, in the invention of claim 1, the DPF arranged in the exhaust passage of the engine for collecting PM in the exhaust gas and the PPF for estimating the PM combustion amount of the DPF.
M combustion amount estimating means, PM inflow estimating means for estimating the PM inflow discharged from the engine and flowing into the DPF,
Regeneration determining means for determining whether the DPF is in the regeneration region, and excess air for increasing the excess air ratio of the engine when the DPF is in the regeneration region and the PM combustion amount is smaller than the PM inflow amount. And a rate control means to configure an exhaust gas purification device for an internal combustion engine.

The "PM inflow amount" here is a PM amount flowing into the DPF per unit time, and is equivalent to a PM amount discharged from the engine per unit time. Also,
The “PM combustion amount” is the amount of PM burned in the DPF per unit time. According to a second aspect of the present invention, the PM combustion amount estimating means estimates the PM combustion amount from the PM accumulation amount of the DPF.

In the third aspect of the present invention, the PM combustion amount estimating means determines the P based on the exhaust pressure on the upstream side of the DPF.
The feature is that the M combustion amount is estimated. In this case, DP
The PM combustion amount may be directly estimated from the exhaust pressure on the upstream side of F, or the PM deposition amount may be obtained from the exhaust pressure on the upstream side of the DPF and estimated from this PM deposition amount. According to the invention of claim 4, an oxidation catalyst is provided which is arranged in the exhaust passage on the upstream side of the DPF and oxidizes NO in the exhaust gas to NO2.

According to a fifth aspect of the present invention, the DPF carries an oxidation catalyst on the surface of the filter.

[0010]

According to the invention of claim 1, when the PM combustion amount in the DPF is smaller than the PM inflow amount in the regeneration region of the DPF, the excess air ratio is corrected so as to increase the excess air ratio. Amount of PM emitted, that is, DPF
The PM inflow amount into the DPF can be reduced, and it is possible to prevent the DPF from being clogged due to inflow of PM in excess of the PM combustion amount in the DPF.

Further, since the excess air ratio is corrected only in the DPF regeneration region (mainly the high load region) and the excess air ratio is not corrected in the region where regeneration does not occur (low load region), at the time of low load. It is possible to prevent the engine from stopping due to an excessive air ratio, and prevent the engine from discharging more PM than the PM combustion amount in the DPF at the time of high load to block the DPF.

According to the invention of claim 2 and / or claim 3, the PM combustion amount can be obtained by a simple method, and the control can be simplified. According to the invention of claim 4 and / or claim 5, NO in the exhaust gas is oxidized to NO2 due to the oxidation function, and this NO2 reacts with PM in the DPF, so that P
M can be removed. And PM and N here
The reaction with O2 is the temperature at which PM reacts with O2 (600
Since it occurs from a temperature lower than (° C. or higher) (for example, 350 ° C.), the regeneration region of the DPF can be expanded to the medium load side.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a compression ignition internal combustion engine (here, a diesel engine) showing a first embodiment of the present invention.
FIG. In the diesel engine 1,
Air passes through an intake throttle valve 3 interposed in the intake passage 2,
It flows into the combustion chamber of each cylinder. Fuel is directly injected into the combustion chamber of each cylinder by a common rail fuel injection device including a high-pressure fuel pump 4, a common rail 5, and a fuel injection valve 6 of each cylinder. The air that has flowed into the combustion chamber of each cylinder and the injected fuel burn here by compression ignition, and the exhaust gas flows out to the exhaust passage 7.

Here, in the exhaust passage 7, a DPF 8 for collecting PM in the exhaust is arranged in the middle thereof. An engine control unit (hereinafter referred to as ECU) 10 includes a rotation speed sensor 11 for detecting an engine rotation speed Ne, an accelerator opening sensor 12 for detecting an accelerator opening APO, and an intake air amount Wair for controlling the engine 1. Air flow meter 13, exhaust pressure sensor 14 for detecting exhaust pressure Pexh
Etc., the signal is input.

The exhaust pressure sensor 14 is connected to the DPF 8 of the exhaust passage 7.
It is provided on the upstream side and is used for estimating the PM accumulation amount of the DPF 8. The ECU 10 performs arithmetic processing based on these input signals, and outputs a fuel injection command signal for controlling the fuel injection amount and injection timing to the fuel injection valve 6 of the common rail fuel injection device according to the operating state. ,Also,
An opening degree instruction signal is output to the intake throttle valve 3.

Next, the correction control of the excess air ratio by the ECU 10 in the above configuration will be described with reference to a flowchart. FIG. 2 is a flow chart of the excess air ratio correction control routine, and this routine is executed every predetermined time.
At S1, the engine speed Ne, the fuel injection amount Qf, the intake air amount Wair, and the exhaust pressure Pexh are read. Here, since the fuel injection amount Qf is calculated based on a map corresponding to the engine speed Ne and the accelerator opening APO, the calculated value is read.

In S2, the fuel injection amount Qf and the intake air amount Wair
And the engine speed Ne, the current excess air ratio λ0
Is calculated by λ0 = (Wair / Ne) / (Qf × 14.7). In S3, referring to the map of FIG. 3, based on the engine speed Ne and the fuel injection amount Qf,
It is determined whether or not it is a regeneration area (self-regeneration area; high load area) of the DPF 8.

If it is not in the regeneration region, the excess air ratio correction control is not performed, so this routine is ended. In the case of the regeneration region, the process proceeds to S4 and S4 for the excess air ratio correction control.
Then, as the PM deposition amount in the DPF 8 increases, the DPF
8 Because the exhaust pressure Pexh on the upstream side increases, the DPF
8 The PM accumulation amount W1 is estimated from the exhaust pressure Pexh on the upstream side. However, since the exhaust pressure Pexh changes depending on the operating state of the engine, it goes without saying that the base exhaust pressure corresponding to the current operating state is taken into consideration.

In next step S5, the PM combustion amount V1 per unit time in the DPF 8 is estimated from the PM accumulation amount W1 in the DPF 8 with reference to the table of FIG. This portion corresponds to PM combustion amount estimation means. Next, in S6, referring to the table of FIG. 5, from the current excess air ratio λ0 to DP
The PM inflow amount V0 per unit time to F8 is estimated.
This portion corresponds to the PM inflow amount estimation means.

In the next step S7, the amount of PM flowing into the DPF 8 (PM inflow amount V0) and the PM removed by combustion in the DPF 8
(PM combustion amount V1) is compared, and if the inflowing amount is larger (V0 ≧ V1), the process proceeds to S8. S8
Then, referring to the table of FIG. 5, the excess air ratio is increased to obtain the excess air ratio λ1 at which the PM inflow amount becomes equal to the PM combustion amount V1 and control the excess air ratio to λ1. . This portion corresponds to the excess air ratio control means.

On the other hand, when the amount of inflow is smaller (V0
In the case of <V1, since the excess air ratio correction control is not performed, this routine is ended. As described above, by controlling the excess air ratio to λ1, the PM inflow amount becomes equal to the PM combustion amount, so that clogging of the DPF 8 can be prevented. Also,
In S8, the excess air ratio may be controlled to λ2 larger than λ1. In this case, since the PM inflow amount is smaller than the PM combustion amount, the DPF 8 is regenerated.

The control of the excess air ratio in S8 is performed by controlling the fuel injection amount. In the case of this embodiment,
This is because the regeneration region is specified as the high load region, and the intake throttle valve 3 is controlled to be fully open in this region. Therefore, the fuel injection amount is reduced and corrected to increase the excess air ratio. In this case, if the fuel injection amount is reduced, the torque may also decrease, but if the air excess ratio is made slightly larger, the generation of smoke is drastically reduced. Therefore, the decrease amount of the fuel injection amount here is very small. Therefore, the torque is not significantly reduced.

Next, a second embodiment of the present invention will be described. FIG. 6 is a system diagram of the internal combustion engine in the second embodiment. The difference from the first embodiment is that the DPF 8 in the exhaust passage 7 is
The point is that the oxidation catalyst 9 is arranged on the upstream side, and the oxidation catalyst is carried on the filter surface of the DPF 8 to form a DPF with an oxidation function. In this case, NO in the exhaust gas is oxidized to NO2 by the oxidation catalyst 9 and the oxidation function of the DPF 8 (the function of the oxidation catalyst carried on the filter), and this NO2
The PM can be removed by reacting with the PM in the DPF 8.

Since the reaction between PM and NO2 occurs here at a lower temperature (350 ° C.) than the reaction between PM and O2, the regeneration region spreads to the medium load side as shown in FIG. Here, the continuous regeneration region shown in FIG. 7 is a region where PM can be removed by the reaction with NO2. The correction control of the excess air ratio in the second embodiment is basically based on the flow of FIG. 2, but the following points are different.

In S3, it is judged whether or not it is the reproduction area.
In the second embodiment, referring to the map of FIG. 7, whether or not the regeneration area (self-regeneration area + continuous regeneration area; medium to high load area) of the DPF 8 is determined based on the engine speed Ne and the fuel injection amount Qf. To judge. In S8, the excess air ratio is increased by obtaining the excess air ratio λ1 with which the PM inflow amount is equal to the PM combustion amount V1 by referring to the table of FIG. 5 and controlling the excess air ratio to λ1. However, the control of the excess air ratio in the second embodiment is performed as follows.

In the case of the self-regeneration region, it is a high load region, and since the intake throttle valve 3 is fully opened in this region, the excess air ratio is controlled only by the fuel injection amount. In the case of the continuous regeneration region, since it is the medium load region, the excess air ratio is controlled by controlling the opening degree of the intake throttle valve 3 and controlling the fuel injection amount.

[Brief description of drawings]

FIG. 1 is a system diagram of an internal combustion engine showing a first embodiment of the present invention.

FIG. 2 is a flowchart of excess air ratio correction control.

FIG. 3 is a map for determining a reproduction area

FIG. 4 Table for estimating PM combustion amount

FIG. 5: Table for estimating PM inflow

FIG. 6 is a system diagram of an internal combustion engine showing a second embodiment of the present invention.

FIG. 7 is a map for reproduction area determination in the second embodiment.

[Explanation of symbols]

1 engine 2 Intake passage 3 intake throttle valve 6 Fuel injection valve 7 exhaust passage 8 DPF 9 Oxidation catalyst 10 ECU 11 Speed sensor 12 Accelerator position sensor 13 Air flow meter 14 Exhaust pressure sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/24 F01N 3/24 E B01D 46/42 B // B01D 46/42 46/46 46/46 53 / 36 103CF Term (reference) 3G090 AA01 BA01 DA00 DA03 DA09 DA18 3G091 AA02 AA18 AB02 AB13 BA07 CB07 HA15 4D019 AA01 BC07 CB04 CB09 4D048 AA06 AA14 AB01 CD05 DA01 DA01 4D04 MA08 DA41 MA44 DA08 MA04 DA01

Claims (5)

[Claims] 1. A particulate filter arranged in an exhaust passage of an engine for collecting particulates in exhaust gas; a particulate combustion amount estimating means for estimating a particulate combustion amount in the particulate filter; Particulate inflow amount estimation means for estimating the amount of particulate inflow that is discharged and flows into the particulate filter, regeneration determining means for determining whether or not the particulate filter is in the regeneration region, and there is in the regeneration region. An exhaust gas purification apparatus for an internal combustion engine, comprising: an excess air ratio control means for increasing an excess air ratio of the engine when the particulate combustion amount is smaller than the particulate inflow amount. 2. The particulate combustion amount estimating means comprises:
The exhaust emission control device for an internal combustion engine according to claim 1, wherein the particulate combustion amount is estimated from the particulate accumulation amount of the particulate filter. 3. The particulate combustion amount estimating means comprises:
The exhaust emission control device for an internal combustion engine according to claim 1, wherein the particulate combustion amount is estimated based on the exhaust pressure on the upstream side of the particulate filter. 4. The oxidation catalyst, which is arranged in the exhaust passage upstream of the particulate filter and oxidizes NO in the exhaust gas into NO2, according to any one of claims 1 to 3. Exhaust gas purification device for internal combustion engine. 5. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the particulate filter carries an oxidation catalyst on the filter surface.