JP2003201885A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize post injection and intake air throttling for regeneration of DPF 14. <P>SOLUTION: For increasing the temperature of DPF 14, this device increases HC amount in the exhaust gas by post injection using a fuel injection valve 9 and rapidly elevate the temperature of DPF 14 to regenerative temperature. After regenerative temperature is reached, the device increases CO amount in the exhaust gas by using an intake air throttle valve 5 to control the exhaust gas λ to the set point. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an exhaust emission control device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as an exhaust gas purification device for an internal combustion engine,
For example, the technique disclosed in Japanese Patent Laid-Open No. 2001-115883 is known. This conventional technique has a function of oxidizing an inflowing exhaust gas component and a particulate (P
The exhaust gas purifying means having a function of trapping M) (function as a diesel particulate filter DPF) is provided, and when the trap amount of PM exceeds a predetermined value (DP
At the F regeneration timing), post injection is performed and the exhaust throttle valve (or the intake throttle valve) is fully closed to raise the temperature of the exhaust gas purification means and perform DPF regeneration.

[0003]

By the way, when the exhaust purification means has an oxidizing function as in the prior art, the heat of oxidation of HC in the exhaust gas (compared to the heat of oxidation of CO) is required to raise the temperature of the exhaust purification means. It has a great influence, and as the amount of HC in the exhaust increases, the heat of oxidation increases, and the temperature of the exhaust purification means can be raised effectively.

In this case, FIG. 9 shows the amounts of HC and CO with respect to changes in the excess air ratio (exhaust gas λ) of the exhaust gas due to the intake throttle.
0, HC and CO for changes in exhaust λ due to post injection
As shown in FIG. 9, the amount of HC in the exhaust gas is sensitive to the change in the exhaust gas λ due to the post injection (FIG. 10), but is insensitive to the change in the exhaust gas λ due to the intake throttle (FIG. 9). ). Therefore, even if the exhaust λ is the same, the amount of HC in the exhaust changes due to the sharing of the post injection and the intake throttle when realizing the exhaust λ.

However, in the above conventional technique, the DPF
At the time of raising the temperature of the exhaust gas purification means for regeneration, the sharing of post injection and intake throttle is not considered at all,
There were the following problems. As shown in FIG.
At the time of PF regeneration, comparing the state where the share of the intake throttle valve is larger (regeneration state A) and the state where the share of post injection is larger (regeneration state B), if the exhaust λ is the same, the exhaust gas The temperature of the purification means becomes higher in the regeneration state B (c, d in the figure), and if the temperature of the exhaust purification means is the same, the exhaust gas λ
Is smaller in the reproduction state A (e and f in the figure).

[0006] Therefore, in the above-mentioned prior art, in the DPF regeneration, the post-injection may be too large in some cases,
There is a risk that the temperature of the exhaust gas purification means becomes too high and melts the exhaust gas purification means, or that the intake throttle valve has too large a share and the exhaust gas λ is too small so that PM cannot be burned and DPF regeneration cannot be performed. An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine that solves the above conventional problems.

[0007]

For this reason, according to the invention of claim 1, the exhaust gas purification means is provided in the exhaust passage of the engine and has a function of oxidizing the inflowing exhaust gas component, and the exhaust gas purification means flows into the exhaust gas purification means. The exhaust gas excess ratio (exhaust gas λ) of the exhaust gas can be changed, and the first exhaust control means in which the temperature change width of the exhaust gas purification means caused by this change is large, and the air excess of the exhaust gas flowing into the exhaust gas purification means. The second exhaust control means that can change the rate (exhaust gas λ) and has a small temperature change range of the exhaust gas purification means that accompanies this change, and the second exhaust gas control means when the temperature of the exhaust gas purification means matches the target temperature. When the exhaust control means No. 1 is selected and the excess air ratio of the exhaust gas flowing into the exhaust purification means is made equal to the target excess air ratio, the second
Selecting means for selecting the exhaust control means of.

According to the second aspect of the invention, when the first exhaust control means is selected, the amount of HC in the exhaust gas flowing into the exhaust purification means is changed mainly, and the second exhaust control means is selected. When this is done, the amount of CO in the exhaust flowing into the exhaust purification means is mainly changed. Claim 3
In the invention, the first exhaust control means includes a fuel supply means capable of supplying fuel into the exhaust gas.

According to a fourth aspect of the present invention, the second exhaust control means includes an intake throttle valve that changes the amount of air taken in by the engine. In the invention of claim 5, the second exhaust control means changes the amount of EGR gas recirculated from the exhaust passage of the engine to the intake passage of the engine.
It is characterized by including a valve.

In a sixth aspect of the present invention, the selecting means sets the temperature of the exhaust gas purifying means to match a target temperature,
The second exhaust control means is selected until the HC oxidizing function of the exhaust purification means is activated. In the invention of claim 7, the selecting means preferentially selects the first exhaust control means at the time of temperature rise prior to the regeneration of the exhaust gas purification means, and the second exhaust control means at the time of regeneration after the temperature rise. Is preferentially selected.

According to an eighth aspect of the invention, the selecting means preferentially selects the second exhaust control means when releasing the sulfur (S) poisoning of the exhaust purification means. To do. In the invention of claim 9, the exhaust gas purification means has a function as a filter for collecting particulates in the exhaust gas and a function as a catalyst, and the regeneration request of the filter and the regeneration request of the catalyst are simultaneously performed. If it is done, the filter is preferentially regenerated.

[0012]

According to the invention of claim 1, when the temperature of the exhaust gas purification means is made to coincide with the target temperature, particularly when the temperature of the exhaust gas purification means deviates from the target temperature, the first exhaust gas control is performed. By selecting the means, the temperature of the exhaust gas purification means can be controlled without changing the exhaust gas λ. Further, when the exhaust λ coincides with the target exhaust λ, particularly when the exhaust λ deviates from the target value, the temperature of the exhaust purification means can be almost changed by selecting the second exhaust control means. Instead, the exhaust λ can be controlled.

According to the second aspect of the present invention, the control of increasing the amount of HC with a large amount of heat generation and the control of increasing the amount of CO with a small amount of heat generation are switched, so that the temperature of the exhaust gas purification means can be maintained at the same exhaust gas λ. It is possible to change or change the exhaust gas λ at the same temperature. According to the third aspect of the present invention, the amount of HC in the exhaust can be controlled mainly by supplying the fuel into the exhaust by post injection or the like, and the amount of HC that generates a large amount of heat can be controlled to change the exhaust λ too much. It is possible to change the temperature of the exhaust gas purification means without performing the above.

According to the fourth aspect of the invention, the amount of CO mainly in the exhaust gas can be controlled by the intake throttle, and the amount of heat generated is small.
By controlling the O amount, the exhaust gas λ can be changed without changing the temperature of the exhaust gas purification means. According to the invention of claim 5, the amount of CO in the exhaust gas can be mainly controlled by the EGR, and the exhaust gas λ can be changed without changing the temperature of the exhaust gas purification means by controlling the CO amount with a small heat generation amount. .

According to the sixth aspect of the invention, when the temperature of the exhaust gas purification means is made to coincide with the target temperature, H of the exhaust gas purification means
Until the C oxidation function is activated, the second exhaust control means is selected to increase the amount of CO in the exhaust, thereby increasing the time for raising the temperature of the exhaust purification means to the target temperature. It can be controlled in the shortest time. This is because the temperature at which the activation of the CO oxidation function (the state where the CO purification rate exceeds 50%) is lower is lower than the temperature at which the activation of the HC oxidation function (the state where the HC purification rate exceeds 50%) occurs. Therefore, at low temperatures, it is a good idea to utilize the oxidation heat of CO to raise the temperature of the exhaust gas purification means.

According to the invention of claim 7, when regenerating the exhaust gas purifying means, the regeneration time can be shortened by giving priority to the temperature rise over the exhaust gas λ until the recyclable temperature is reached. After reaching, it is possible to prevent melting loss during regeneration by giving priority to control of the exhaust gas λ. According to the invention of claim 8, when the S-poisoning of the exhaust purification means is released, the S-poisoning cannot be released in the lean atmosphere. Therefore, the desorption of S is made by giving priority to the control of the exhaust λ. It becomes possible to promote.

According to the invention of claim 9, when the request for regeneration of the filter and the request for regeneration of the catalyst are made at the same time, the regeneration of the filter is preferentially performed, that is, the exhaust gas pressure is increased to improve the engine performance. By prioritizing the regeneration of the filter that directly affects the driving performance, deterioration of drivability can be suppressed.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of an internal combustion engine (here, a diesel engine) showing an embodiment of the present invention. The intake passage 2 of the diesel engine 1 is provided with an intake compressor of a variable nozzle turbocharger 3, and intake air is supercharged by the intake compressor.
After being cooled by the intercooler 4, passing through the intake throttle valve 5, it flows into the combustion chamber of each cylinder through the collector 6.
The fuel is pressurized by the common rail fuel injection device, that is, by the high-pressure fuel pump 7 and sent to the common rail 8, and is directly injected from the fuel injection valve 9 of each cylinder into the combustion chamber. The air that has flowed into the combustion chamber and the injected fuel burn here by compression ignition, and the exhaust gas flows out to the exhaust passage 10.

A part of the exhaust gas flowing into the exhaust passage 10 is E
The GR gas is returned to the intake side by the EGR passage 11 via the EGR valve 12. The rest of the exhaust gas passes through the exhaust turbine of the variable nozzle type turbocharger 3 and drives it. Here, downstream of the exhaust turbine in the exhaust passage 10, for purification of exhaust gas, NOx in the exhaust gas is trapped when the air-fuel ratio of the inflowing exhaust gas is lean, and trapped when the air-fuel ratio of the inflowing exhaust gas is rich. A NOx trap catalyst 13 that desorbs and purifies NOx is arranged. Further, this NOx trap catalyst 13 is a NOx trap catalyst with an oxidation function, which has a function of supporting a noble metal and oxidizing HC and CO in the exhaust gas.

Further, downstream of the NOx trap catalyst 13, a filter (hereinafter referred to as DPF) 14 for collecting particulates (hereinafter referred to as PM) in exhaust gas is arranged. Further, the DPF 14 has a three-way catalyst supported thereon to have a function of oxidizing HC and CO in the exhaust gas and a function of reducing NOx, thereby forming a three-way function DPF. The NOx trap catalyst 13 and the DPF 14 may be arranged in reverse, or the DPF may carry the NOx trap catalyst and may be integrally configured.

To control the engine 1, signals are input to the control unit 20 from a rotation speed sensor 21 for detecting the engine speed Ne and an accelerator opening sensor 22 for detecting the accelerator opening APO. Further, a catalyst temperature sensor 23 that detects the temperature of the NOx trap catalyst 13 (catalyst temperature), an exhaust pressure sensor 24 that detects the exhaust pressure at the DPF 14 inlet side of the exhaust passage 10, and a DPF that detects the temperature of the DPF 14 (DPF temperature). A temperature sensor 25 and an air-fuel ratio sensor 26 for detecting an excess air ratio (hereinafter referred to as exhaust λ) of exhaust are provided on the DPF 14 outlet side of the exhaust passage 10, and these signals are also input to the control unit 20. However, the temperature of the NOx trap catalyst 13 and the temperature of the DPF 14 may be indirectly detected from the exhaust temperature by providing an exhaust temperature sensor on the downstream side thereof.

Based on these input signals, the control unit 20 performs the main injection by the fuel injection valve 9 and the fuel injection amount and injection timing of the post injection performed after the main injection (expansion stroke or exhaust stroke) under predetermined operating conditions. It outputs a fuel injection command signal to the fuel injection valve 9 for control, an opening command signal to the intake throttle valve 5, an opening command signal to the EGR valve 12, and the like.

Here, the control unit 20
Then, desorption and purification of NOx trapped and accumulated in the NOx trap catalyst 13, sulfur (S) poisoning of the NOx trap catalyst 13 for burning and removing S accumulated therein (poison removal), and trapped in the DPF 14. Exhaust gas purification control for burning and removing the accumulated PM (DPF regeneration) is performed, and the exhaust gas purification control will be described in detail below.

2 to 8 are flowcharts of exhaust gas purification control executed by the control unit 20. First, a description will be given along the flow of FIG. At S1, various sensor signals are read, engine speed Ne, accelerator opening A
PO, catalyst temperature, DPF inlet side exhaust pressure, DPF temperature,
The DPF outlet side exhaust λ is detected. Further, the main injection amount Q calculated from the map using the engine speed Ne and the accelerator opening APO as parameters is read.

In S2, the NOx accumulation amount trapped and accumulated in the NOx trap catalyst is calculated. Here, for example, as in the calculation of the NOx absorption amount described in Japanese Patent Publication No. 2600492, page 6, it is estimated from the integrated value of the engine speed. In S3, the amount of S accumulation accumulated on the NOx trap catalyst due to S poisoning is calculated. Here, as in the calculation of the NOx accumulation amount, the estimation is made from the integrated value of the engine speed.

At step S4, the amount of PM accumulated in the DPF and accumulated is calculated as follows. When the PM deposition amount of the DPF increases, the exhaust pressure on the DPF inlet side naturally rises. Therefore, the exhaust pressure sensor detects the exhaust pressure on the DPF inlet side, and the current operating state (engine speed Ne, fuel injection amount Q) The PM deposition amount is estimated by comparison with the reference exhaust pressure in. In addition, by combining the mileage from the previous DPF regeneration, the engine speed integrated value, and the exhaust pressure,
The PM deposition amount may be estimated.

In S5, it is determined whether or not the reg1 flag indicating that the temperature raising mode during DPF regeneration is being set. When the reg1 flag = 1, the control proceeds to the temperature increase mode control of FIG. 3 described later. In S6, it is determined whether or not the reg2 flag indicating that the combustion mode during DPF regeneration is set. When the reg2 flag = 1, the control proceeds to the combustion mode control of FIG. 4 described later.

In step S7, it is determined whether or not the reg3 flag indicating that the melting damage prevention mode during DPF regeneration is set. If the reg3 flag = 1, the process proceeds to control of the melting loss prevention mode of FIG. 5 described later. At S8, re indicating that the NOx trap catalyst is in the S-poisoning release mode is re.
It is determined whether or not the g4 flag is set. When the reg4 flag = 1, the process proceeds to S poisoning release mode control of FIG. 6 described later.

At S9, it is determined whether or not the reg5 flag indicating that the DPF is in the energy saving regeneration mode is set. If reg5 flag = 1, the process proceeds to the energy saving regeneration mode control of FIG. 7, which will be described later. In S10, it is determined whether or not the sp flag indicating that the NOx desorption purification of the NOx trap catalyst is in the rich spike mode is set. If sp = 1, the process proceeds to the rich spike mode control of FIG. 8 described later.

In S11, PM of DPF calculated in S4
Whether the DPF regeneration timing is reached after the accumulation amount exceeds the predetermined value PM1 (exhaust pressure on the DPF inlet side exceeds the exhaust pressure threshold value corresponding to the current operating state (Ne, Q) shown in FIG. 12) judge. If it is determined that the PM accumulation amount> PM1 and the DPF regeneration time is reached, the DPF regeneration is started.
Proceed to 2 and set the reg1 flag = 1.

In S13, it is determined whether or not the S accumulation amount of the NOx trap catalyst calculated in S3 exceeds the predetermined value S1 and the S poisoning release timing has come. S accumulation amount> S1, N
If it is determined that the S poisoning release timing of the Ox trap catalyst is reached, the process proceeds to S14 to start S poisoning removal, and re
Set the g4 flag = 1.

In S15, the NOx accumulation amount of the NOx trap catalyst calculated in S2 exceeds the predetermined value NOx1, and NO
x It is determined whether the desorption purification time has come. When NOx accumulation amount> NOx1, and when it is determined that the NOx desorption purification timing is reached, the routine proceeds to S16, where it is determined whether the catalyst temperature exceeds a predetermined temperature (lower limit temperature that can be purified by the rich spike) Tlower. , If the catalyst temperature> Tlower, then N
S1 for rich spike control for Ox desorption purification
7 and sets sp flag = 1.

It should be noted that the determination of the regeneration timing of the DPF (S13, S15) is made based on the determination of the regeneration timing of the NOx trap catalyst (S13, S15).
By performing 11) first, it is possible to suppress an increase in exhaust pressure that tends to affect drivability. In S18, the DPF
It is determined whether the temperature is equal to or higher than the predetermined temperature T5.
The predetermined temperature T5 is, for example, 400 ° C., and if it is higher than this, the DPF can be regenerated by adding a small amount of energy to the DPF, and thus energy saving regeneration can be performed.

In S19, it is determined whether the PM accumulation amount is larger than the predetermined value PM2. The relationship of PM2 <PM1 is satisfied, and although it is not the perfect regeneration time, it is determined whether or not the PM accumulation amount PM2 that can obtain sufficient regeneration efficiency by setting the regeneration mode is reached. For example, the exhaust pressure threshold value of 50 shown in FIG.
If it is more than%, it is judged that the energy saving regeneration is performed.

At S20, the DPF temperature is higher than T5,
Since it is determined that the PM accumulation amount is also larger than PM2, the reg5 flag = 1 is set to start the energy saving regeneration mode. Next, the control of the first temperature rising mode during DPF regeneration will be described. When it is determined in step S11 of the flow of FIG. 2 that the PM accumulation amount> PM1 and the DPF regeneration timing is determined, the reg1 flag = 1 is set in step S12, and from the next time, the temperature increase mode of FIG. Go to control of.

The control of the temperature raising mode of FIG. 3 will be described. In S31, the DPF temperature is a predetermined temperature T1 (HC oxidation function activation in the oxidation catalyst (HC purification rate of 50%
It is determined whether the temperature is higher than 400 ° C.). When the DPF temperature is T1 or lower, the routine proceeds to S32, where the exhaust λ is controlled to a predetermined λ1 (≧ 1) by controlling the intake throttle valve (or EGR valve).
That is, by controlling the exhaust λ with the intake throttle, CO having a high reactivity (CO reacts more easily at low temperature when HC does not oxidize) is discharged from the engine,
Raise the DPF temperature.

However, although CO has a low reaction temperature, thermal energy is small and it is often difficult to raise the temperature of the DPF to a level at which it can be regenerated. On the other hand, if post-injection is used, since the thermal energy of HC (fuel) is large, it is possible to easily raise the temperature of the DPF and the catalyst. As shown in FIG. 9, the intake throttle (or EG
R) is used to change the exhaust λ, C
The amount of O fluctuates greatly. However, since the thermal energy of CO is 1/4 or less that of HC, it is difficult to increase the temperature of the DPF significantly.

As shown in FIG. 10, when the exhaust λ is changed by using post injection, the amount of HC greatly changes with respect to the amount of post injection, but the change of CO is small. However, if the exhaust λ is changed only by the post injection, the amount of HC may be significantly increased, and the temperature of the DPF and the catalyst may be excessively increased. That is, even if the exhaust gas λ is the same as shown in FIG. 11, the temperatures of the catalyst and the DPF are significantly different between when the CO is positively discharged by the intake throttle and when HC is emitted by the post injection (FIG. 11). a ~
d).

In the regeneration of the DPF or the NOx trap catalyst, the target exhaust gas λ is the same, but the target bed temperature is different. Therefore, for example, when the bed temperature reaches the target, the exhaust gas λ is adjusted by the intake air. If the exhaust λ reaches the target and the bed temperature deviates from the target by performing the throttle, it is necessary to utilize post injection to suppress the fluctuation of the exhaust λ and control the bed temperature. Therefore, intake throttle and EGR
Due to CO and H due to post injection
By controlling C, the target exhaust λ and the bed temperature can be realized at the same time.

Therefore, when the DPF temperature exceeds T1,
For the first time, the processing proceeds to S33 and S34 and then to S35, as shown in FIG.
As shown in, the amount of post injection determined by the engine operating state (Ne, Q) is executed to raise the DPF temperature by the oxidation reaction of the oxidation catalyst carried by the DPF. After that, in S33, it is determined whether or not the time tpost from the start of the post injection or the change of the post injection amount exceeds the predetermined value tst1, and if tpost> tst1, the process proceeds to S34. Although the temperature of the DPF is increased by the post injection, the DPF has a thermal inertia.
This determination is made because the time tst1 is required for the PF temperature to change.

At S34, the DPF temperature is the predetermined temperature T2.
It is determined whether or not (the temperature at which the DPF can be regenerated, for example, 650 ° C.) is exceeded. If the DPF temperature is below T2, S
The process proceeds to 35 and the post injection amount is increased. If the DPF temperature exceeds T2, the process proceeds to S36 to end the temperature raising mode, so the reg1 flag is set to 0 and S37 is performed.
Reg2 flag =
Set to 1.

Next, the combustion mode after temperature rise during DPF regeneration will be described. When the reg2 flag = 1 is set in S37 of FIG. 3, from the next time, S6 of FIG.
Proceed to the control of the combustion mode of. The control of the combustion mode of FIG. 4 will be described. In this combustion mode control, oxygen is supplied to the DPF to regenerate it as the DPF temperature rises to a temperature at which PM combustion is possible.

At S41, the exhaust throttle valve is controlled to control the exhaust λ to a target value according to the PM accumulation amount as shown in FIG. Specifically, the opening of the intake throttle valve is controlled so that the target intake air amount according to the engine operating state (Ne, Q) as shown in FIG.
Is deviating from the target value, the opening degree of the intake throttle valve is adjusted to match. Although the intake throttle valve controls the exhaust λ here, the EGR valve may be used instead of the exhaust throttle valve λ.
Alternatively, the EGR valve may be used together for control.

At S42, the DPF temperature is controlled within a predetermined temperature range (T21 to T22). When the opening degree of the intake throttle valve is changed in S41, the DPF temperature deviates from the target value (T2). If the DPF temperature deviates from the predetermined temperature range due to this deviation, the post injection amount is increased / decreased to a predetermined value. Return to temperature range. Here, T21 is set to 600 ° C. as the lower limit temperature at which the DPF can be regenerated, and T22 is set to 700 ° C. as the upper limit temperature at which the DPF does not melt.

In S43, after performing the control in S41 and S42, it is determined whether or not a predetermined time tdpfreg1 enough to burn and remove the PM accumulated in the DPF has elapsed. Predetermined time t
When dpfreg1 has elapsed, it is considered that the PM accumulated in the DPF has been burned and removed, and in S44, the post injection is stopped and the heating of the DPF is stopped. In S45, the combustion mode has ended, so the reg2 flag is set to 0. In S46, the combustion mode has ended, but the PM unburned residue is D.
When the exhaust gas λ is suddenly increased while in the PF, PM may be burned in the DPF all at once and melted. Therefore, the reg3 flag = 1 is set in order to enter the melted damage prevention mode.

Next, the melt loss prevention mode after combustion during DPF regeneration will be described. Reg3 flag = S46 in FIG.
When set to 1, from next time, the process proceeds from S7 of the flow of FIG. 2 to the control of the melting loss prevention mode of FIG. Control of the melting loss prevention mode of FIG. 5 will be described. In S51, since the DPF temperature is extremely high because it is immediately after regeneration or immediately after high-load operation, the exhaust throttle λ and EGR are used to prevent exhaust λ
Is controlled to the value shown in FIG.

In S52, it is determined whether the DPF temperature is lower than the temperature T3 (= 500 ° C.) at which PM oxidation does not start. In S53, there is no risk of melting damage to the DPF, so the exhaust λ control is stopped. In step S54, the erosion prevention mode has ended, so the reg3 flag is set to 0. Then N
The control at the time of releasing S poisoning of the Ox trap catalyst will be described.

When it is determined in S13 of the flow in FIG. 2 that the S accumulation amount> S1 and the S poisoning release timing is determined,
The reg4 flag = 1 is set in S14, and from the next time, S
8 to the control of the S poisoning release mode of FIG. S in FIG.
The control of the poisoning release mode will be described. In S61,
Since the S accumulation amount of the catalyst has reached a predetermined amount, the exhaust λ is controlled stoichiometrically by controlling the intake throttle valve. Specifically, the intake air is throttled so as to reach the target intake air amount for the stoichiometric operation shown in FIG. 13 to reach the target λ = 1,
If it deviates from the target λ = 1, intake throttle and EG
The exhaust λ is adjusted using R.

In addition, the first time, through S62 and S63, S
Proceed to 64 to perform post injection. Then, in S62,
Time tpost from start of post injection or change of post injection amount
Is greater than a predetermined value tst2, and tpost> tst
In the case of 2, proceed to S63. Incidentally, tst2 is set according to the heat capacity of the carrier of the NOx trap catalyst. In S63, it is determined whether the catalyst temperature has exceeded the predetermined temperature T4. For example, when a Ba-based NOx trap catalyst is used, it is necessary to set the temperature to 600 ° C. or higher in a rich to stoichiometric atmosphere, so T4 is set to 600 ° C. or higher.

When the catalyst temperature is T4 or lower, the process proceeds to S64 and the post injection amount is increased. Exhaust gas λ fluctuates due to the change in the post injection amount, but the target exhaust gas λ and the target bed temperature can be realized by adjusting the intake air amount again in S61. If the catalyst temperature exceeds T4, the process proceeds to S65. In S65, it is determined whether or not the predetermined time tdesu1 has elapsed while the catalyst temperature exceeds T4, in other words, whether or not the S poisoning removal processing has been performed at the target exhaust λ and the bed temperature.

At S66, since the S poison release is completed, the stoichiometric operation is released. In S67, the S-poisoning release mode has ended, so the reg4 flag = 0 is set. Next DPF
The control of the energy-saving regeneration will be described. When it is determined that the DPF temperature> T5 and the PM accumulation amount> PM2 in S18 and 19 of the flow of FIG. 2 and the energy saving regeneration time is determined, the reg5 flag = 1 is set in S20, and from the next time, S9 is set. To control of the energy-saving reproduction mode of FIG.

The control of the energy saving reproduction mode of FIG. 7 will be described. In S71, the exhaust throttle valve (or EGR valve) is controlled to control the exhaust λ to a target value according to the PM accumulation amount as shown in FIG. In S72, it is determined whether the DPF temperature has reached the combustion start temperature T2. In S73, D
When the PF temperature is lower than T2, a predetermined amount of post injection is executed in S74. When the DPF temperature is higher than T2, it is determined whether a predetermined regeneration time tdpfreg1 has elapsed,
When the time has passed, the process proceeds to S75 and thereafter.

In S75, the post injection is stopped. S7
In 6, the reg5 flag = 0 is set because the energy-saving reproduction mode has ended. In step S77, the reg3 flag = 1 is set because the mode is shifted to the melting loss prevention mode. Next, rich spike control for NOx desorption purification of the NOx trap catalyst will be described.

By the determinations in S15 and S16 of the flow of FIG.
NOx accumulation amount> NOx1, catalyst temperature> Tlower,
If it is determined that it is the NOx desorption purification time, sp is executed in S17.
The flag is set to 1, and from next time, the process proceeds from S10 to the control of the rich spike mode of FIG. The control in the rich spike mode of FIG. 8 will be described.

In S81, the intake throttle valve is controlled to control the target intake air amount for the rich spike operation in accordance with the engine operating state (Ne, Q) shown in FIG. 15 to perform the rich spike. In S82, it is determined whether a predetermined time tsp has elapsed in the rich spike state. In S83,
Since rich spike has been performed for a predetermined time, rich operation is canceled.

At S84, the rich spike flag sp =
Set to 0 to end the rich spike mode.

[Brief description of drawings]

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

FIG. 2 is a flowchart of exhaust purification control (No. 1)

FIG. 3 is a flowchart of exhaust purification control (No. 2)

FIG. 4 is a flowchart (part 3) of exhaust gas purification control.

FIG. 5 is a flowchart of exhaust purification control (No. 4)

FIG. 6 is a flowchart of exhaust purification control (No. 5)

FIG. 7 is a flowchart of exhaust purification control (6).

FIG. 8 is a flowchart of exhaust purification control (No. 7)

FIG. 9 is a diagram showing exhaust components when exhaust λ is changed by an intake throttle.

FIG. 10 is a diagram showing exhaust components when exhaust λ is changed by post injection.

FIG. 11 is a characteristic diagram when the shares of intake throttle and post injection are different.

FIG. 12 is a map showing the exhaust pressure threshold value of the DPF.

FIG. 13 is a map showing a target intake air amount for stoichiometric operation.

FIG. 14 is a map showing a target intake air amount for preventing DPF melting damage.

FIG. 15 is a map showing a target intake air amount for rich spike operation.

FIG. 16 is a map showing a unit post injection amount for raising the temperature.

FIG. 17 is a table showing target exhaust λ during regeneration with respect to PM deposition amount.

[Explanation of symbols]

1 diesel engine 2 Intake passage 5 intake throttle valve 9 Fuel injection valve 10 exhaust passage 12 EGR valve 13 NOx trap catalyst with oxidation function 14 DPF with ternary function 20 control unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/20 F01N 3/20 E 3G301 3/24 3/24 ER S 3/36 3/36 A F02D 9/02 F02D 9/02 Q 21/08 301 21/08 301A 43/00 301 43/00 301E 301N 45/00 312 45/00 312R F02M 25/07 550 F02M 25/07 550R 570 570J F term (reference) 3G062 AA01 AA03 AA05 BA04 BA05 BA06 CA06 DA01 DA02 EA04 EA10 ED01 ED04 ED10 FA02 FA05 FA06 FA23 GA04 GA06 GA09 GA17 GA22 3G065 AA01 AA03 AA04 CA12 DA04 BA07 BA10 BA04 BA04 BA04 BA08 GA04 GA08 GA08 GA08 GA08 GA04 GA08 HA08 GA04 GA08 GA04 GA08 GA04 GA08 GA04 GA08 GA04 GA08 GA08 GA04 GA08 GA04 GA04 GA08 GA04 GA08 GA04 BA08 BA04 BA04 GA04 GA08 GA04 GA08 GA04 GA08 GA10 GA46 HA04 GA04 GA08 GA04 GA10 GA46 GA08 GA04 GA08 GA04 BA08 BA10 BA46 GA08 GA04 GA08 BA04 BA04 BA04 BA08 GA10 GA46 HA04 GA04 DA28 EB08 EB12 FA07 FA10 FA13 FA18 FA26 FA27 FA28 FA33 FA37 3G091 AA02 AA10 AA11 AA18 AA28 AB01 AB02 AB03 AB13 BA04 BA08 BA11 BA14 BA1 5 BA19 CB02 DA10 DB10 DC07 EA01 EA03 EA05 EA07 EA08 EA17 EA18 EA34 FB01 FB09 FC07 FC08 HA08 HA10 HA15 HA36 HA37 HA42 HB05 HB06 3G092 AA02 AA06 AA17 FA06 EA01 FA15 FA06 EA01 FA01 DC01 DC01 DC08 DE08 DC01 DC01 DC08 DC08 DC01 DC08 HA11Z HB01X HD02X HD02Z HD04X HD07X HE01Z 3G301 HA02 HA04 HA06 HA11 HA13 JA21 JA24 JA25 JA26 JA33 LA01 LB12 NA08 NC02 NC04 ND03 ND07 NE13 PA01A PA01Z PA11A PA11Z PA18Z PB03Z PD12A PD15A PE01Z

Claims (9)

[Claims] Claim: What is claimed is: 1. An exhaust gas purifying device, which is disposed in an exhaust passage of an engine and has a function of oxidizing an inflowing exhaust gas component, and an excess air ratio of exhaust gas flowing into the exhaust gas purifying device. A first exhaust control unit that has a large temperature change width of the exhaust gas purification unit that accompanies it, and an excess air ratio of the exhaust gas that flows into the exhaust gas purification unit can be changed, and the temperature of the exhaust gas purification unit that occurs due to this change A second exhaust control means having a small change width, and the first exhaust control means when the temperature of the exhaust purification means is made to coincide with a target temperature, and the excess air ratio of the exhaust gas flowing into the exhaust purification means is selected. An exhaust emission control device for an internal combustion engine, comprising: a selection unit that selects the second exhaust control unit when the target excess air ratio is met. 2. When the first exhaust control means is selected, the amount of HC in the exhaust flowing into the exhaust purification means is mainly changed, and when the second exhaust control means is selected, the HC amount in the exhaust gas is changed. The exhaust gas purification device for an internal combustion engine according to claim 1, wherein the amount of CO in the exhaust gas flowing into the exhaust gas purification means is mainly changed. 3. The exhaust purification of an internal combustion engine according to claim 1 or 2, wherein the first exhaust control means includes a fuel supply means capable of supplying fuel into exhaust gas. apparatus. 4. The second exhaust control means is configured to include an intake throttle valve that changes the amount of air taken in by the engine. An exhaust emission control device for an internal combustion engine as set forth in. 5. The second exhaust control means comprises an EGR valve for changing the amount of EGR gas recirculated from the exhaust passage of the engine to the intake passage.
The exhaust emission control device for an internal combustion engine according to claim 4. 6. The selection means sets H of the exhaust purification means when the temperature of the exhaust purification means matches a target temperature.
The first exhaust control means is selected until the C oxidation function is activated.
2. An exhaust gas purification device for an internal combustion engine according to any one of 1. 7. The selecting means preferentially selects the first exhaust control means at the time of temperature rise prior to the regeneration of the exhaust gas purification means, and gives priority to the second exhaust control means at the time of regeneration after the temperature rise. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 6, characterized in that the exhaust gas purification device is selectively selected. 8. The selection means preferentially selects the second exhaust control means when releasing sulfur poisoning of the exhaust purification means. 2. An exhaust gas purification device for an internal combustion engine according to any one of 1. 9. The exhaust gas purification means has a function as a filter for collecting particulates in exhaust gas and a function as a catalyst, and a request for regeneration of the filter and a request for regeneration of the catalyst are made at the same time. In this case, the exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 8, wherein the regeneration of the filter is performed with priority.