JP3412459B2 - Engine exhaust purification device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control system for an engine, and more particularly to an exhaust emission control system for preventing hydrocarbons (HC) contained in exhaust gas immediately after starting the engine from being released into the atmosphere.

[0002]

2. Description of the Related Art Immediately after a cold engine start, the exhaust gas temperature is low and does not reach the temperature at which the three-way catalyst is activated (around 300 ° C.), so that HC (hydrocarbon) is hardly purified. Therefore, an HC adsorption catalyst is provided in the exhaust system,
There is a system in which HC discharged without being purified immediately after a cold start is adsorbed to this adsorption catalyst, and then HC is desorbed from the adsorption catalyst and burned (Japanese Patent Laid-Open No. 6-661).
No. 36).

[0003]

However, in the conventional apparatus, by repeating the adsorption of HC to the adsorbent and the desorption of HC from the adsorbent, a part of the HC inside the adsorbent causes so-called coking. The HC that has caused this coking (hereinafter referred to as coking HC) cannot be desorbed even if desorption treatment is performed, and accumulates in the adsorbent. When this coking HC is exposed to high temperature exhaust gas due to sudden acceleration or the like under desorption conditions, there is a possibility of burning in the adsorbent.
In particular, when adsorption and desorption are repeated for a long period of time and a large amount of coking HC is accumulated, the temperature of the adsorbent may rise to 1000 ° C. or more due to the combustion, which may cause deterioration of the adsorbent. .

Therefore, the present invention is based on the coking H for the adsorbent.
By estimating the amount of C deposited and burning the coking HC by raising the temperature of the adsorbent to the combustible temperature of HC before the amount of depositing the caulking HC increases.
The purpose is to prevent the temperature of the adsorbent from rising abnormally.

[0005]

[0006]

A first invention is an HC adsorbent and the adsorbent.
Means for supplying secondary air upstream of the adsorbent and downstream of the adsorbent
Equipped with a catalyst with heating means located at
Adsorbs HC discharged from the engine when it is warm to the adsorbent
In addition, the HC desorbed from this adsorbent is
Oxidized by the catalyst in an activated state using secondary air.
In the exhaust emission control device for the engine,
Means for estimating the amount of coking HC deposited on the adsorbent,
When this estimated value exceeds a specified value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
And a means for performing the regeneration process of the
Branch into the bypass passage, and use the secondary air passage in this bypass passage.
Air supply means, the adsorbent, the catalyst with the heating means,
A valve means capable of adjusting the ratio of the exhaust gas flowing through the both passages
While each is provided, the valve means is controlled by the adsorption condition.
By introducing all the exhaust gas into the bypass passage
Adsorption treatment and heating of the adsorbent under desorption conditions
The desorption process is performed by and the deposition amount of the coking HC on the adsorbent is estimated from the number of times the adsorption process and the desorption process are performed.

A second invention is an HC adsorbent and the adsorbent.
Means for supplying secondary air upstream of the adsorbent and downstream of the adsorbent
Equipped with a catalyst with heating means located at
Adsorbs HC discharged from the engine when it is warm to the adsorbent
In addition, the HC desorbed from this adsorbent is
Oxidized by the catalyst in an activated state using secondary air.
In the exhaust emission control device for the engine,
Means for estimating the amount of coking HC deposited on the adsorbent,
When this estimated value exceeds a specified value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
And a means for performing the regeneration process of the
Branch into the bypass passage, and use the secondary air passage in this bypass passage.
Air supply means, the adsorbent, the catalyst with the heating means,
A valve means capable of adjusting the ratio of the exhaust gas flowing through the both passages
While each is provided, the valve means is controlled by the adsorption condition.
By introducing all the exhaust gas into the bypass passage
Adsorption treatment and heating of the adsorbent under desorption conditions
The period during which the adsorbent adsorbs HC in the exhaust gas (for example, time) while the desorption process is performed by
From this, the amount of coking HC deposited on the adsorbent is estimated. A third invention is an HC adsorbent and an upstream of the adsorbent.
Means for supplying secondary air and located downstream of the adsorbent
And a catalyst with heating means for
When the HC discharged from the engine is adsorbed by the adsorbent,
At the same time, the HC desorbed from this adsorbent is removed from the secondary space.
To oxidize with the catalyst in the activated state using air
In the exhaust gas purification device for the engine,
For estimating the amount of coking HC deposited in
When the value exceeds a certain value, up to the HC combustible temperature
Regeneration of the adsorbent by raising the temperature of the adsorbent
And the exhaust pipe is bypassed to the main passage.
Branch to the passage and use this bypass passage to supply the secondary air.
Stage, the adsorbent, the catalyst with heating means, and both
Each valve means that can adjust the proportion of exhaust gas flowing in the passage
On the other hand, the valve means is controlled by the adsorption condition while the valve is installed.
Adsorption processing by introducing the entire amount of exhaust gas into the ipas passage
By heating the adsorbent under desorption conditions
The desorption process is performed, and the amount of coking HC deposited on the adsorbent is estimated from the total amount of air during the period when the adsorbent adsorbs HC in the exhaust gas.

In a fourth aspect of the invention, the total air amount is estimated from the engine speed and the suction negative pressure during the period in which the adsorbent adsorbs HC in the exhaust gas in the third aspect of the invention.

[0010]

A fifth invention is an HC adsorbent and the adsorbent.
Means for supplying secondary air upstream of the adsorbent and downstream of the adsorbent
Equipped with a catalyst with heating means located at
Adsorbs HC discharged from the engine when it is warm to the adsorbent
In addition, the HC desorbed from this adsorbent is
Oxidized by the catalyst in an activated state using secondary air.
In the exhaust emission control device for the engine,
Means for estimating the amount of coking HC deposited on the adsorbent,
When this estimated value exceeds a specified value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
Exhaust pipe without branch
With the secondary air supply means, the adsorbent, and the heating means
A catalyst is provided , and H in the exhaust gas is adsorbed on the adsorbent.
Caulking HC to the adsorbent from the number of times C is adsorbed
Estimate the amount of deposits.

A sixth invention is an HC adsorbent and the adsorbent.
Means for supplying secondary air upstream of the adsorbent and downstream of the adsorbent
Equipped with a catalyst with heating means located at
Adsorbs HC discharged from the engine when it is warm to the adsorbent
In addition, the HC desorbed from this adsorbent is
Oxidized by the catalyst in an activated state using secondary air.
In the exhaust emission control device for the engine,
Means for estimating the amount of coking HC deposited on the adsorbent,
When this estimated value exceeds a specified value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
Exhaust pipe without branch
With the secondary air supply means, the adsorbent, and the heating means
A catalyst is provided , and H in the exhaust gas is adsorbed on the adsorbent.
The deposition amount of coking HC on the adsorbent is estimated from the period (for example, time) during which C is adsorbed.

A seventh invention is an HC adsorbent and the adsorbent.
Means for supplying secondary air upstream of the adsorbent and downstream of the adsorbent
Equipped with a catalyst with heating means located at
Adsorbs HC discharged from the engine when it is warm to the adsorbent
In addition, the HC desorbed from this adsorbent is
Oxidized by the catalyst in an activated state using secondary air.
In the exhaust emission control device for the engine,
Means for estimating the amount of coking HC deposited on the adsorbent,
When this estimated value exceeds a specified value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
Exhaust pipe without branch
With the secondary air supply means, the adsorbent, and the heating means
A catalyst is provided , and H in the exhaust gas is adsorbed on the adsorbent.
The deposition amount of coking HC on the adsorbent is estimated from the total air amount during the period when C is adsorbed.

In an eighth aspect of the present invention, the total air amount is estimated from the engine speed and suction negative pressure during the period in which the adsorbent adsorbs HC in the exhaust gas in the seventh aspect .

According to a ninth aspect of the invention, in any one of the first to fourth aspects of the invention, the exhaust gas is introduced into the bypass passage by controlling the valve means when the temperature of the exhaust gas is high.
The temperature of the adsorbent is raised.

In a tenth aspect of the present invention, in any one of the first to eighth aspects of the present invention, the adsorbent is provided with a heating means, and the heating means is operated to raise the temperature of the adsorbent. .

In an eleventh invention, in any one of the first to eighth inventions, the secondary air supply means is provided with a heating means, and the adsorbent is raised by operating the heating means. Do warm.

In a twelfth invention, in the tenth or eleventh invention, the heating means is an electric heater.

In a thirteenth aspect of the present invention, in any one of the tenth to twelfth aspects of the present invention, the regeneration treatment is performed after the completion of the desorption of HC.

In a fourteenth aspect of the invention, in the thirteenth aspect of the invention, the adsorbent is heated to the first predetermined value to complete the desorption of HC, and subsequently a second value larger than the first predetermined value. The regeneration process is performed by raising the temperature of the adsorbent to a predetermined value. The fifteenth invention is engine exhaust.
It is installed in a pipe and adsorbs HC at low temperature and exceeds a certain temperature.
And the HC adsorbent that desorbs HC,
Coking H to the adsorbent from the number of times HC is adsorbed
A means for estimating the amount of C accumulation and this estimated value is equal to or greater than a predetermined value.
When the temperature becomes
Regeneration of the adsorbent by raising the temperature of the adsorbent
And means for making it happen. The sixteenth invention relates to an engine
It is installed in the exhaust pipe and adsorbs HC at low temperature and exceeds a certain temperature.
HC adsorbent that desorbs HC when exhausted, and exhaust to this adsorbent
Cakin to the adsorbent from the period of adsorbing HC in the
Means for estimating the amount of accumulated HC and this estimated value is a predetermined value
When the above is reached, up to the combustible temperature of the caulking HC
Regeneration of the adsorbent by raising the temperature of the adsorbent
And a means to do the work. The seventeenth invention is an engine
It is installed in the exhaust pipe of the engine and adsorbs HC at low temperature to maintain a constant temperature.
HC adsorbent that desorbs HC when it exceeds the
From the total amount of air during the period when HC in the exhaust gas is adsorbed, the adsorption
Means for estimating the amount of coking HC deposited on the agent, and
Combustion of coking HC when the estimated value exceeds a predetermined value
By increasing the temperature of the adsorbent to a possible temperature
And means for regenerating the adsorbent.

[0021]

In the first to third inventions, the amount of coking HC deposited on the adsorbent is estimated, and the adsorbent is regenerated before the amount of coking HC deposited increases. It is possible to avoid a situation in which a large amount of deposited coking HC is exposed to high temperature exhaust gas due to sudden acceleration under desorption conditions and burns inside the adsorbent, causing an abnormal temperature rise in the adsorbent. Even if caulking HC remains inside, the deterioration of the adsorbent can be suppressed.

If the number of times the adsorption process and the desorption process are performed as in the first aspect of the invention (or the number of adsorption times as in the eighth aspect), the period during which the adsorption condition is satisfied is short but long. However, the amount of deposition of coking HC on the adsorbent is larger when the adsorption conditions are satisfied for a longer time. Therefore, if the adsorption condition is satisfied for a relatively long time and a predetermined value is set for comparison with the number of times the adsorption process and desorption process are performed, the adsorption condition is actually satisfied only for a relatively short time. If not, the regeneration process is performed (useless regeneration is performed) even though the amount of coking HC deposited is not so large, but in the second and sixth inventions, the HC in the exhaust gas is absorbed. Since the deposition amount of the coking HC on the adsorbent is estimated from the period of time , the estimation accuracy of the deposition amount of the coking HC is improved as compared with the first invention,
As a result, it is not necessary to perform unnecessary reproduction processing.

Even if the adsorption time is the same, when the amount of air flowing during the adsorption period is large, caulking HC to the adsorbent is obtained.
The amount of deposits increases. Therefore, when the amount of air flowed is smaller than the amount of air when the predetermined value for comparison with the period of adsorbing HC was matched, the regeneration process is performed although the amount of coking HC accumulated is not so large ( but wasted a reproduction is performed) that, third and
In each invention of No. 7 , since the amount of coking HC deposited on the adsorbent is estimated from the total air amount during the adsorption period, even if the operating conditions (rotation speed and load) change during the adsorption period, It is possible to accurately estimate the deposition amount of coking HC.

In both the desorption process and the regeneration process, when the heating means of the adsorbent or the secondary air supply means is operated to raise the temperature of the adsorbent, the regeneration process is performed after a certain time from the completion of desorption. If this is done, electric power will be consumed each time the temperature of the adsorbent is raised. However, in the thirteenth invention, the regeneration process is performed following the desorption end without a delay between the desorption end and the regeneration start. Therefore, if the operating conditions from the desorption process to the regeneration process are the same, it is only necessary to add the power required to raise the temperature required for desorption (300 ° C) to the temperature required for regeneration (600 ° C). Playback is possible,
This can reduce the power consumption for the reproduction process.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is an engine body, 2 is an exhaust pipe, 3 and 4 are three-way catalysts. Incidentally, 4 may be a combination of a reduction catalyst and an oxidation catalyst.

The exhaust pipe 2 is provided downstream of the three-way catalyst 4 with the main passage 2a.
And a valve 5 for switching the flow of exhaust gas to the main passage 2a and the bypass passage 2b. The switching valve 5 is driven by the control unit 11 directly or via an actuator (not shown).

In the bypass passage 2b, the adsorbent 6 and the heater-equipped catalyst 7 supply the secondary air in this order from the upstream side, and also immediately upstream of the adsorbent 6, so that the air supply passage 8 and the air pump are provided. A secondary air supply device consisting of 9 is installed respectively.

Here, the adsorbent 6 is a honeycomb simple substance coated with a slurry containing zeolite powder as a main component, and the adsorbent 6 adsorbs HC at a low temperature and exceeds the constant temperature (about 300 ° C.). It has the property of being detached.

In order to detect the exhaust temperature downstream of the three-way catalyst,
A temperature sensor 12 is provided on the upstream side of the switching valve 5. A temperature signal from the sensor 12 is input to a control unit 11 including a microcomputer, and the control unit 11 controls the switching valve 5, the catalyst 7 with a heater, and the air pump 9 based on the temperature signal to adsorb and desorb HC. Each of the three processes of separating and cleaning the separated HC is performed.

Since methods for adsorbing and desorbing HC and purifying HC are known (Japanese Patent Laid-Open No. 6-1014).
No. 52), the description based on the flowchart is omitted, and the contents are outlined.

The three-way catalysts 3 and 4 provided on the upstream side of the exhaust pipe 2 carry a noble metal (platinum, rhodium, etc.) or other metals, and are harmful components in the exhaust gas in an active state around 300 ° C. Purifies certain HC, CO, and NOx at the same time (oxidizes HC and CO and reduces NOx).

However, the temperature of the exhaust gas is low immediately after the cold start of the engine 1, and the activation temperature (30
Since it does not reach 0 ° C.), the HC in the exhaust gas is not purified by the three-way catalysts 3 and 4 and flows into the exhaust pipe 2 downstream. The exhaust temperature at this time is detected by the sensor 12 and input to the control unit 11. In the control unit 11, the exhaust temperature detected by the sensor 12 is compared with a predetermined temperature (for example, 300 ° C.), and when the exhaust temperature is lower than the predetermined temperature, the main passage 2a is closed with respect to the switching valve 5 and the bypass passage 2b is opened. The drive signal is output to open. As a result, the entire amount of exhaust gas flows into the bypass passage 2b, and the adsorbent 6 traps HC. At this time, the catalyst with heater 7 is in a non-energized state, and the air pump 9 is in a non-operated state.

After that, when the three-way catalysts 3 and 4 are activated,
The exhaust gas temperature downstream of the three-way catalysts 3 and 4 rises. When the exhaust temperature exceeds the above predetermined temperature, the control unit 11 outputs a drive signal to the switching valve 5 to close the bypass passage 2b and open the main passage 2a, and to the catalyst 7 with a heater. To start energizing. By this operation, the exhaust gas purified by the three-way catalysts 3 and 4 is discharged through the main passage 2a. At this time, the adsorbent 6 is still trapping HC.

When the catalyst 7 with a heater rises to the activation temperature (for example, 350 ° C.) by energization, H
In order to desorb C, the switching valve 5 is controlled so that the bypass passage 2b side is partially (or entirely) opened, and hot exhaust gas is caused to flow into the bypass passage 2b. At the same time, the air pump 9 is operated to introduce the secondary air into the bypass passage 2b via the air supply passage 8. Guide the hot exhaust gas to H from the adsorbent 6
At the same time as desorbing C, the desorbed HC is purified by oxidation treatment in the catalyst 7 with a heater by using oxygen existing in a large amount in the secondary air. The desorption process of the HC from the adsorbent and the purification process with the heater-equipped catalyst are terminated when a predetermined time has elapsed.

Whether or not the heater-equipped catalyst 7 has been activated is determined by the time during which the heater-equipped catalyst 7 is energized.
Of course, the temperature of the catalyst 7 with a heater is detected by a temperature sensor provided inside or downstream of the catalyst 7 with a heater, and it is determined whether or not the catalyst 7 with a heater is activated by comparing the detected temperature with a predetermined temperature. It is also possible to do so.

Here, the exhaust gas temperature being lower than a predetermined temperature is an adsorption condition which will be described later, and the fact that the catalyst 7 with a heater is raised to an activation temperature is a desorption condition which will be described later.

Now, the adsorption of HC on the adsorbent 6 and the adsorbent 6
Repeated desorption of HC from the so-called caulking H
C remains inside the adsorbent 6, and caulking H to this adsorbent
The amount of C deposited gradually but gradually increases. Then, the amount of this accumulation becomes large, and this large amount of coking HC is
Under desorption conditions, it is exposed to hot exhaust gas due to sudden acceleration, etc.
If burned all at once, the temperature of the adsorbent becomes high, which may cause deterioration.

To deal with this, in the first embodiment of the present invention, the amount of coking HC deposited on the adsorbent is estimated,
Before the coking HC to the adsorbent increases, the adsorbent is regenerated.

The contents of this control executed by the control unit 11 will be described with reference to the following flow chart.

FIG. 2 is for determining whether or not the regeneration processing of the adsorbent is performed, which is performed at regular time intervals.

Assuming that the flow of FIG. 2 is entered, the regeneration processing flag FSS is initialized to "0" at the time of starting (when the ignition key switch is switched from OFF to ON), and the adsorption / desorption number counter CKYU is set. When the engine last stopped (ON to OFF of ignition key switch)
(At the time of switching to) is held.

In step 1, adsorption / desorption number counter C
KYU is compared with a predetermined value CKYUS. Here, the counter CKYU is incremented by 1 each time adsorption and desorption are performed by a flow not shown.
Caulking HC to adsorbent by repeating adsorption and desorption
Therefore, the amount of coking HC deposited is estimated from the number of times of adsorption and desorption. Since the adsorption is performed while the adsorption condition is satisfied and the desorption process is performed while the desorption condition is satisfied, the adsorption process and the desorption process over the predetermined period are performed once. It goes without saying that the number of desorption times is reached. In addition, the coking HC refers to one of the adsorbed HC that remains without being desorbed in the desorption process, and basically the adsorption and desorption are performed as a set, so the expression "adsorption / desorption count" is used. Are using.

When CKYU ≧ CKYUS, it is determined that the coking HC has accumulated on the adsorbent at an allowable value or more (that is, the regeneration process is required), the process proceeds to step 2, and the regeneration process flag FSS is set to "1". Set to ", CKY
If U <CKYUS, then FSS is reset to "0" in step 3. FSS = 1 indicates that the reproducing process is necessary, and FSS = 0 indicates that the reproducing process is not necessary.

FIG. 3 is for performing reproduction processing.
After that, it is executed at regular intervals.

In steps 11, 12, 13, 14, and 15, the following conditions <1> FSS = 1 (step 11), <2> adsorption conditions (step 12), <3> desorption conditions (step). 13), <4> Exhaust gas temperature TEXH ≧ predetermined value T
EXHS (eg, 600 ° C.) (step 14)
As a result, when any of the conditions is not satisfied (that is, when the reproduction condition is not satisfied), the current operation is ended as it is.
When the condition of <1> is not satisfied, the reproduction process is not required in the first place. When the conditions of <2> and <3> are not satisfied, the reproduction process cannot be performed, so that the condition of <4> is not satisfied. This is because it is impossible to burn the coking HC even if the exhaust gas is guided (when the exhaust gas temperature is low). The exhaust temperature TEXH in <4> may be directly detected by the sensor 12 or may be estimated from operating conditions.

When all the above conditions are satisfied (when the reproduction condition is satisfied), the process proceeds to step 15 and it is determined whether or not the reproduction is completed based on the elapsed time after the reproduction process is started.

If the reproduction has not ended, step 16
Then, the switching valve 5 is controlled so that the bypass passage 2b side is partially opened so that the high temperature exhaust gas flows into the bypass passage 2b. At the same time, the air pump 9 is operated to introduce the secondary air into the bypass passage 2b via the air supply passage 8.
The high temperature exhaust gas is guided to set the adsorbent 6 to a predetermined value (for example, 600
C.) and the coating HC deposited on the adsorbent 6 is burned inside the adsorbent using oxygen existing in a large amount in the secondary air to regenerate the adsorbent 6. .

On the other hand, when the adsorbent regeneration process is completed, the process proceeds from step 15 to steps 17, 18 and 19 to perform post-treatments in the regeneration process (the switching valve 5 is driven so that the bypass passage 2b is fully closed). Then, the operation of the air pump 9 is stopped, the regeneration processing flag FSS is reset to "0" to indicate that the regeneration processing is completed, and the adsorption / desorption number counter CKYU is reset to 0).

As described above, in the first embodiment, the deposition amount of coking HC on the adsorbent is estimated from the number of adsorption and desorption of HC in the exhaust gas, and adsorption is performed before the deposition amount of coking HC increases. Since the agent is regenerated, a large amount of accumulated coking HC is exposed to high temperature exhaust gas due to sudden acceleration under desorption conditions and burns inside the adsorbent, causing an abnormal temperature rise in the adsorbent. This can be avoided, and even if caulking HC remains inside the adsorbent, deterioration of the adsorbent can be suppressed.

The flow charts of FIGS. 4 and 5 are the second embodiment and correspond to FIGS. 2 and 3 of the first embodiment, respectively.
In FIGS. 4 and 5, the same parts as those in FIGS. 2 and 3 are designated by the same step numbers.

While the first embodiment estimates the amount of coking HC deposited on the adsorbent from the number of adsorption and desorption, the second embodiment
In the embodiment, the deposition amount of coking HC is estimated from the time when the adsorbent adsorbs HC in the exhaust gas.

The parts different from the first embodiment will be mainly described. First, on the assumption that the flow of FIG. 4 is entered, the second embodiment also starts (when the ignition key switch is turned off).
(When switching from ON to ON), the reproduction processing flag FSS is "0".
Is set to 0 and the adsorption time counter TKYU is set at the last engine stop (ignition key switch O
(At the time of switching from N to OFF).

In FIG. 4, in step 21, it is determined whether or not the adsorption condition is satisfied, and only when the adsorption condition is satisfied, the process proceeds to step 22 and the adsorption time counter TKYU is incremented, and this counter TKYU and the predetermined value TKY.
Compare with US in step 23. TKYU ≧ T
If it is KYUS, reproduction processing is necessary, so the routine proceeds to step 2, where reproduction processing flag FSS = 1 is set, and TKY is set.
If U <TKYUS (reproduction processing is not yet required), FSS = 0 is set in step 3.

Next, FIG. 5 differs from FIG. 3 only in step 31, in which the adsorption time counter TKYU is reset to zero.

As for the number of times of adsorption and desorption as in the first embodiment, the adsorption condition is satisfied once even if the period during which the adsorption condition is satisfied is short or long. When this happens, the amount of coking HC deposited on the adsorbent increases. Therefore, when the predetermined value CKYUS in step 1 of FIG. 2 is set assuming that the adsorption condition is satisfied for a relatively long time, and when the adsorption condition is actually satisfied for a relatively short time, the deposition amount of the coking HC is not so great. However, the reproduction process is performed (useless reproduction is performed) even though there are not many.

On the other hand, in the second embodiment, the amount of coking HC deposited on the adsorbent is estimated from the time when the HC in the exhaust gas is adsorbed by the adsorbent. The estimation accuracy of the accumulation amount is improved, and thus unnecessary regeneration processing is not performed.

The flowcharts of FIGS. 6 and 7 are the third embodiment and correspond to FIGS. 4 and 5 of the second embodiment, respectively.
6 and 7, the same parts as those in FIGS. 4 and 5 are designated by the same step numbers.

In the third embodiment, the amount of coking HC deposited on the adsorbent is estimated from the total amount of air flowing during the period when the adsorbent adsorbs HC in the exhaust gas.

The difference from the second embodiment will be mainly described.
First, on the premise that the flow of FIG. 6 is entered, also in the third embodiment, the regeneration process flag FSS is initialized to "0" at the time of starting, and the adsorption air amount counter CAIR is set to the value when the last engine stop (ignition key switch ON to O
(At the time of switching to FF).

When the adsorption condition is satisfied, the routine proceeds from step 21 to step 41, where CAIR = CAIR (old) + Ne × (Pa-Boo)
st) However, the adsorbing air amount counter is updated by the formula of CAIR (old): previous CAIR Ne: engine speed Pa: atmospheric pressure Boost: suction negative pressure.

At the time of adsorption, the exhaust temperature is in a low operating region (low load region), and the air amount per predetermined period in this operating region is proportional to the product of Ne and (Pa-Boost). The total amount of air at the time of adsorption is obtained by adding up (amount of air per unit) over the adsorption period.

The adsorption air amount counter C thus updated
The AIR and the predetermined value CAIRS are compared in step 42. If CAIR ≧ CAIRS, the process proceeds to step 2 to set the reproduction process FSS = 1, and CAIR <CAI.
If RS, proceed to step 3 and set FSS = 0.

Next, FIG. 7 differs from the second embodiment in step 51, in which CAIR is reset to 0.

Even when the adsorption period is the same, the amount of coking HC deposited on the adsorbent is larger when the amount of air flowing during the adsorption period is larger. Therefore, when an air amount smaller than the air amount at the time of matching the predetermined value TKYUS in step 23 of FIG. 4 flows, the regeneration processing is performed although the coking HC accumulation amount is not so large (useless regeneration is performed. Will be told).

On the other hand, in the third embodiment, the coking H to the adsorbent is calculated from the total amount of air actually flowing during the adsorption period.
Since the amount of C deposited is estimated, even if the operating conditions (rotation speed and load) change during the adsorption period, coking HC to the adsorbent
It is possible to accurately estimate the deposition amount of.

8 and 9 show a fourth embodiment, which correspond to FIGS. 1 and 3 of the first embodiment, respectively. FIG. 2 is also used as it is in the fourth embodiment. The same parts as those in FIGS. 1 and 3 are designated by the same reference numerals and step numbers.

In the first embodiment, the temperature of the adsorbent for the desorption process and the regeneration process is raised by guiding the exhaust gas to the bypass passage when the exhaust gas is at a high temperature. An electric heater is provided, and the adsorbent 21 is heated by energizing the adsorbent heater. As a result, also in the fourth embodiment, the same operational effects as in the first embodiment can be obtained.

The method of raising the temperature of the adsorbent is not limited to this, and when the air pump has a heater, the high temperature secondary air is introduced into the bypass passage by energizing the heater to adsorb the adsorbent. The agent can be heated.

The difference from the first embodiment will be mainly described with reference to FIG. 9. When the regeneration condition is satisfied and the regeneration is not completed, the routine proceeds to step 61, where the adsorbent heater is energized and the air pump is operated. When the regeneration is completed, in step 62, the energization of the adsorbent to the heater and the operation of the air pump are stopped. The bypass passage 2b remains fully closed. Also, FIG. 9 does not include step 14 of FIG.

The flowchart of FIG. 10 is the fifth embodiment and corresponds to FIG. 9 of the fourth embodiment. FIG. 8 is also used in this embodiment.

In this embodiment, the regeneration process of the adsorbent is not performed independently of the desorption process, but is performed subsequent to the desorption process. The method for estimating the amount of coking HC deposited on the adsorbent may be the same as in any of the first to fourth embodiments, but here it is the same as in the fourth embodiment (hence the first embodiment). Described in.
Further, the temperature of the adsorbent for desorption and regeneration is explained here by energizing the heater provided in the adsorbent, but the other temperature raising method described above (by energizing the heater provided in the air pump Alternatively, high temperature secondary air may be introduced into the bypass passage, or the exhaust gas may be introduced into the bypass passage by controlling the switching valve when the exhaust gas is hot.

FIG. 10 is for performing each process of desorption and regeneration, which is executed at regular intervals.

At step 71, the flag FSSTYU (initially set to "0" at the time of starting) is checked. This flag FSST
As will be described later, YU is a flag that is set to "1" when reprocessing is required at the timing when desorption is completed, so that FSSTYU = 0 at the beginning of startup. Therefore, in terms of the state at the beginning of starting, the process proceeds to step 72 and subsequent steps from FSSTYU = 0.

Steps 72, 73, 74 and 76 are parts for performing desorption processing. Since the desorption process itself is not important, a brief description will be made. In steps 72 and 73, it is determined whether desorption conditions are satisfied and whether desorption is completed. For example, the desorption condition is satisfied when HC is adsorbed on the adsorbent 21 and the activation of the three-way catalysts 3 and 4 is completed. Further, when the elapsed time from the start of the desorption process exceeds a predetermined value, the desorption ends.

When the desorption condition is satisfied and the desorption is not completed, the routine proceeds to step 74, where the desorption process is performed (the adsorbent heater is energized to set the adsorbent to a predetermined value (for example, 300).
Temperature) to operate the air pump to introduce secondary air and to energize the heater of the catalyst 7 located downstream of the adsorbent).

On the other hand, when the desorption is completed, step 73
Then, the process proceeds to step 75, and the reproduction processing flag FSS is checked. When FSS = 0, the routine proceeds to step 76, where post-treatment of desorption treatment is performed as in the conventional case (stopping the energization of the adsorbent heater, stopping the operation of the air pump, and stopping the energization of the catalyst heater).

When FSS = 1, the process proceeds to step 77,
After the flag FSSTYU is set to "1", the adsorbent heater is continuously energized in step 78 in order to perform the regeneration process, and a predetermined temperature (for example, 600 ° C) higher than the adsorbent temperature at the time of the desorption process is performed. The temperature of the adsorbent is raised and the air pump is operated.

The above-mentioned flag FSSTYU is
When U = 1, it is a flag indicating that the reproduction is in progress subsequent to the desorption end, and when FSSTYU = 0, it is not in the reproduction subsequent to the desorption end. Flag FSS
When TYU is set to "1", the flow from step 71 to step 79 is started from the next time, and it is checked whether or not the reproduction following the end of desorption is completed from the elapsed time after the reproduction processing is started. . If the reproduction following the desorption is not completed, the operation of step 78 is executed.

When the reproduction subsequent to the end of the detachment is completed, the process proceeds to step 80 and thereafter to perform the post-processing (flag F).
Reset both SSTYU and FSS to "0", stop energizing the adsorbent heater, stop the operation of the air pump,
The adsorption / desorption number counter CKYU is reset to 0).

In the fourth embodiment, when the adsorbent heater is energized to raise the temperature of the adsorbent in both the desorption process and the regeneration process, the regeneration is performed with a certain time after the desorption is completed. When processing is performed, electric power is consumed each time the temperature of the adsorbent is raised. On the other hand, the fifth
In the embodiment, since the regeneration process is performed after the desorption end without delaying between the desorption end and the regeneration start, it is necessary for the desorption if the operating conditions from the desorption process to the regeneration process are the same. Regeneration can be performed only by adding power required to raise the temperature from 300 ° C. to a temperature required for regeneration (600 ° C.), thereby reducing power consumption for regeneration processing.

FIGS. 11, 12, and 13 show a sixth embodiment, and FIGS. 11 and 13 correspond to FIGS. 8 and 9 of the fourth embodiment, respectively. Note that FIG. 2 of the first embodiment is also used in the fourth embodiment in its entirety, and FIG. 12 corresponds to this FIG. In FIG. 11, FIG. 12, and FIG.
The same parts as those in FIGS. 2 and 9 are designated by the same reference numerals and step numbers.

The fourth embodiment is the adsorbent 21 with a heater,
The catalyst 7 with a heater and the secondary air supply device (consisting of the air pump 9 and the air supply passage 8) are assumed to be provided in the bypass passage, whereas in the sixth embodiment, these are exhausted without branching. It is assumed that the pipe 2 is provided. Therefore, in this case, since the exhaust gas always flows through the adsorbent 21, the adsorption and desorption are carried out as the exhaust gas temperature rises. That is, the adsorbent 21 is also adsorbed at a low exhaust gas temperature immediately after the start-up because the adsorbent 21 is at a low temperature, the exhaust gas temperature rises with warming up, and the desorption starts when the adsorbent temperature rises. Due to the difference in this premise, the fourth embodiment differs from step 91 in FIG. 12 and steps 92, 9 in FIG.
3 is different, and the deposition amount of coking HC is estimated from the adsorption number counter (which holds the value at the time of the previous engine stop at the time of this start) CKYU2 (step 9 in FIG. 12).
1, step 93 in FIG. 13). Here, the adsorption number counter CKYU2 is incremented by 1 each time the engine is started and adsorption is performed.
It is counted up one by one. Also, FIG.
In step 92 of 3, it is determined whether or not the adsorbent is adsorbing, for example, from the engine cooling water temperature, the exhaust temperature, the adsorbent temperature, or the like.

As described above, although the premise is different from that of the fourth embodiment, the regeneration can be performed by forcibly raising the temperature of the adsorbent by the heater as in the fourth embodiment. The same effects as those of the embodiment can be obtained in the sixth embodiment.

In the sixth embodiment, the case where the temperature of the adsorbent is raised by energizing the adsorbent heater has been described. However, the air pump has a heater, and the temperature of the adsorbent is raised by energizing the heater. You can also

[Brief description of drawings]

FIG. 1 is a control system diagram of a first embodiment.

FIG. 2 is a flowchart for explaining determination of reproduction processing.

FIG. 3 is a flowchart for explaining a reproduction process.

FIG. 4 is a flowchart for explaining determination of reproduction processing according to the second embodiment.

FIG. 5 is a flowchart for explaining a reproduction process of the second embodiment.

FIG. 6 is a flowchart for explaining determination of reproduction processing according to the third embodiment.

FIG. 7 is a flowchart illustrating a reproduction process according to a third embodiment.

FIG. 8 is a control system diagram of a fourth embodiment.

FIG. 9 is a flowchart for explaining a reproduction process of the fourth embodiment.

FIG. 10 is a flowchart for explaining each process of desorption and regeneration of the fifth embodiment.

FIG. 11 is a control system diagram of a sixth embodiment.

FIG. 12 is a flowchart for explaining determination of reproduction processing according to the sixth embodiment.

FIG. 13 is a flowchart for explaining a reproduction process of the sixth embodiment.

[Explanation of symbols]

2 exhaust pipe 6 Adsorbent 7 catalyst with heater 9 Air pump 11 Control unit 12 Exhaust temperature sensor 21 Adsorbent with heater

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F01N 3/24 F01N 3/24 LR (72) Inventor Hirofumi Tsuchida 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A 5-231134 (JP, A) JP-A 5-256124 (JP, A) JP-A 8-14035 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) F01N 3/08-3/24

Claims (17)

(57) [Claims] 1. An HC adsorbent , a means for supplying secondary air upstream of the adsorbent, and a catalyst with a heating means located downstream of the adsorbent.
Well, the HC emitted from the engine when the engine temperature is low
While adsorbing to the adsorbent, desorbing from this adsorbent
The above-mentioned catalyst in the activated state of the incoming HC using the secondary air
In the exhaust purification system of the engine that is made to oxidize by
And means for estimating the amount of coking HC deposited on the adsorbent
And when this estimated value exceeds a predetermined value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
And a means for performing the regeneration process of the exhaust gas , and the exhaust pipe is branched into a main passage and a bypass passage.
The secondary air supply means, the adsorbent, and the heating hand in the passage.
The stepped catalyst and the proportion of the exhaust gas flowing through both passages are adjusted.
Adjustable valve means are provided respectively, but the
The valve means is controlled to guide all the exhaust gas to the bypass passage.
Adsorption treatment by entering the above, and the above adsorption under desorption conditions
Perform desorption treatment by raising the temperature of the agent
Together with the adsorption treatment and to estimate the accumulated amount of coking HC exhaust purification device characteristics and to Rue engine of the number of to perform the desorption process to the adsorbent. 2. An HC adsorbent , a means for supplying secondary air upstream of the adsorbent, and a catalyst with heating means located downstream of the adsorbent.
Well, the HC emitted from the engine when the engine temperature is low
While adsorbing to the adsorbent, desorbing from this adsorbent
The above-mentioned catalyst in the activated state of the incoming HC using the secondary air
In the exhaust purification system of the engine that is made to oxidize by
And means for estimating the amount of coking HC deposited on the adsorbent
And when this estimated value exceeds a predetermined value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
And a means for performing the regeneration process of the exhaust gas , and the exhaust pipe is branched into a main passage and a bypass passage.
The secondary air supply means, the adsorbent, and the heating hand in the passage.
The stepped catalyst and the proportion of the exhaust gas flowing through both passages are adjusted.
Adjustable valve means are provided respectively, but the
The valve means is controlled to guide all the exhaust gas to the bypass passage.
Adsorption treatment by entering the above, and the above adsorption under desorption conditions
Perform desorption treatment by raising the temperature of the agent
Together with the exhaust purification device characteristics and to Rue engine to estimate the accumulated amount of coking HC to the adsorbent from the HC period adsorbed in the exhaust gas to the adsorbent. 3. An HC adsorbent, means for supplying secondary air upstream of the adsorbent, and a catalyst with heating means located downstream of the adsorbent.
Well, the HC emitted from the engine when the engine temperature is low
While adsorbing to the adsorbent, desorbing from this adsorbent
The above-mentioned catalyst in the activated state of the incoming HC using the secondary air
In the exhaust purification system of the engine that is made to oxidize by
And means for estimating the amount of coking HC deposited on the adsorbent
And when this estimated value exceeds a predetermined value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
And a means for performing the regeneration process of the exhaust gas , and the exhaust pipe is branched into a main passage and a bypass passage.
The secondary air supply means, the adsorbent, and the heating hand in the passage.
The stepped catalyst and the proportion of the exhaust gas flowing through both passages are adjusted.
Adjustable valve means are provided respectively, but the
The valve means is controlled to guide all the exhaust gas to the bypass passage.
Adsorption treatment by entering the above, and the above adsorption under desorption conditions
Perform desorption treatment by raising the temperature of the agent
Together with the exhaust purification device characteristics and to Rue engine to estimate the accumulated amount of coking HC to the adsorbent from the total air quantity of the adsorbed HC in the exhaust gas to the adsorbent period. 4. The exhaust gas purifying apparatus for an engine according to claim 3 , wherein the total air amount is estimated from an engine speed and a suction negative pressure during a period in which the adsorbent adsorbs HC in exhaust gas. . 5. An HC adsorbent, means for supplying secondary air to the upstream of the adsorbent, and a catalyst with heating means located downstream of the adsorbent.
Well, the HC emitted from the engine when the engine temperature is low
While adsorbing to the adsorbent, desorbing from this adsorbent
The above-mentioned catalyst in the activated state of the incoming HC using the secondary air
In the exhaust purification system of the engine that is made to oxidize by
And means for estimating the amount of coking HC deposited on the adsorbent
And when this estimated value exceeds a predetermined value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
Means for performing the regeneration process of the secondary air supply means and the adsorption
Agent, wherein together are provided with a heating means with the catalyst, the exhaust from the number of adsorbed HC in the exhaust gas characteristics and to Rue engine to estimate the accumulated amount of coking HC to the adsorbent to the adsorbent Purification device. 6. An HC adsorbent, means for supplying secondary air upstream of the adsorbent, and a catalyst with heating means located downstream of the adsorbent.
Well, the HC emitted from the engine when the engine temperature is low
While adsorbing to the adsorbent, desorbing from this adsorbent
The above-mentioned catalyst in the activated state of the incoming HC using the secondary air
In the exhaust purification system of the engine that is made to oxidize by
And means for estimating the amount of coking HC deposited on the adsorbent
And when this estimated value exceeds a predetermined value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
Means for performing the regeneration process of the secondary air supply means and the adsorption
Agent, wherein together are provided with a heating means with the catalyst, the exhaust from the HC period adsorbed in the exhaust characteristics and to Rue engine to estimate the accumulated amount of coking HC to the adsorbent to the adsorbent Purification device. 7. An HC adsorbent, means for supplying secondary air upstream of this adsorbent, and a catalyst with heating means located downstream of said adsorbent.
Well, the HC emitted from the engine when the engine temperature is low
While adsorbing to the adsorbent, desorbing from this adsorbent
The above-mentioned catalyst in the activated state of the incoming HC using the secondary air
In the exhaust purification system of the engine that is made to oxidize by
And means for estimating the amount of coking HC deposited on the adsorbent
And when this estimated value exceeds a predetermined value, the combustible temperature of HC
The adsorbent by heating the adsorbent up to
Means for performing the regeneration process of the secondary air supply means and the adsorption
Agents, together are provided with the heating means with the catalyst, it and estimates the deposition amount of coking HC from the total amount of air time was adsorbed HC in the exhaust gas to the adsorbent to the adsorbent exhaust emission control device of the engine. 8. The exhaust gas purifying apparatus for an engine according to claim 7 , wherein the total air amount is estimated from an engine speed and a suction negative pressure during a period during which the adsorbent adsorbs HC in the exhaust gas. . By 9. controlling the valve means when the high-temperature exhaust introducing exhaust in the bypass passage, any one of claims 1 to 4, characterized in that the Atsushi Nobori of the adsorbent Exhaust gas purification device for engine according to item 1. 10. The adsorbent is provided with a heating means, and the adsorbent is heated by operating the heating means, according to any one of claims 1 to 8. Exhaust gas purification device for the engine described. 11. with preferably provided with heating means to said secondary air supply means, claim 1, wherein the performing heating of the adsorbent by actuating the heating means
8. An engine exhaust gas purification device according to any one of items 8 to 8 . 12. An exhaust purification device for an engine according to claim 10 or 11, characterized in that said heating means is an electric heater. 13. An exhaust purification device for an engine according to any one of claims 10, characterized in that subsequent to the completion of the desorption of HC performs the reproduction processing up to 12. 14. The temperature of the adsorbent is raised to a first predetermined value to complete the desorption of HC, and subsequently the adsorbent is raised to a second predetermined value larger than the first predetermined value. The exhaust emission control device for an engine according to claim 13 , wherein the regeneration process is performed by heating. 15. Installed in an engine exhaust pipe at low temperature
HC adsorbs HC and desorbs it when the temperature exceeds a certain level.
With adhesive From the number of times HC in exhaust gas is adsorbed by this adsorbent,
Means for estimating the amount of coking HC deposited on the adhesive, When this estimated value exceeds a predetermined value, the caulking HC
By raising the temperature of the adsorbent to the combustible temperature
A means for performing a regeneration process of the adsorbent is provided.
A characteristic engine exhaust purification system. 16. An engine exhaust pipe installed at low temperature
HC adsorbs HC and desorbs it when the temperature exceeds a certain level.
With adhesive From the period when HC in exhaust gas is adsorbed by this adsorbent,
Means for estimating the amount of coking HC deposited on the adhesive, When this estimated value exceeds a predetermined value, the caulking HC
By raising the temperature of the adsorbent to the combustible temperature
A means for performing a regeneration process of the adsorbent is provided.
A characteristic engine exhaust purification system. 17. An engine exhaust pipe installed at low temperature
HC adsorbs HC and desorbs it when the temperature exceeds a certain level.
With adhesive Total air volume during the period when HC in exhaust gas is adsorbed by this adsorbent
The amount of coking HC deposited on the adsorbent from
Means and When this estimated value exceeds a predetermined value, the caulking HC
By raising the temperature of the adsorbent to the combustible temperature
A means for performing a regeneration process of the adsorbent is provided.
A characteristic engine exhaust purification system.